Systems and methods for diagnosing a vehicle engine intake manifold and exhaust system

ABSTRACT

Methods and systems are provided for pinpointing a source of degradation in a vehicle engine system. In one example, a method includes spinning an engine of a vehicle unfueled in a forward and a reverse direction, in no particular order, and recording a first intake air flow and a second intake air flow, respectively, in an intake of the engine, and where the source of degradation is indicated as a function of both the first air flow and the second air flow. In this way, the degradation of the vehicle engine system may be pinpointed as to being located in the intake manifold, the exhaust system, or the engine.

FIELD

The present description relates generally to methods and systems forassessing the presence or absence of degradation in a vehicle engine,engine intake manifold, or engine exhaust system.

BACKGROUND/SUMMARY

Internal combustion engines combust a mixture of fuel and air in orderto produce torque to propel a vehicle. Specifically, air is drawn intothe engine via an engine intake based on a position of a throttle, andthen the air is mixed with fuel. The air-fuel mixture is combustedwithin engine cylinder(s), to drive piston(s) within the cylinder(s),thus rotating an engine crankshaft. By-products of combustion within theengine cylinders are routed to one or more catalysts via an exhaustmanifold, prior to exiting to atmosphere.

Both the engine intake and exhaust systems may exhibit degradation, overtime. Any presence of degradation in the intake manifold, exhaustsystem, or engine may lead to a decrease in fuel economy, and in someexamples may lead to an increase in undesired emissions. The inventorshave herein recognized these issues.

Engine operation may be regulated based on a number of parameters, suchas the air flow rate provided to the engine. A measurement of air flowprovided to the engine may be determined by a mass air flow (MAF)sensor, for example. However, in the intake manifold, any presence ofdegradation downstream of the MAF sensor may result in unmetered airbeing provided to the engine. As a result, the air-fuel ratio may switchlean. However, there are many other root causes for an engine runninglean, such as undesired combustion, exhaust gas oxygen sensors that arenot functioning as desired, valve timing issues, the MAF sensor notfunctioning as desired, etc. Thus, it can be challenging to specificallydiagnose the presence or absence of degradation stemming from an intakesystem or intake manifold downstream of a MAF sensor. Similarly,degradation in the exhaust system may be difficult to pinpoint, if saiddegradation is downstream of an exhaust gas oxygen sensor, for example.

U.S. Patent No. US20090187301 teaches a method of diagnosing thepresence or absence of degradation in an intake manifold of an engine,by comparing manifold absolute pressure to atmospheric pressure. In oneexample, a significant amount of degradation is indicated responsive tomanifold absolute pressure being substantially equivalent to atmosphericpressure.

However, the inventors herein have recognized potential issues with sucha method. For example, such a method is unable to diagnose the presenceor absence of degradation in an exhaust system of the vehicle. Thus, theinventors have herein developed systems and methods to address suchissues. In one example, a method is provided, comprising spinning anengine of a vehicle unfueled in a forward and a reverse direction toobtain a first intake air flow and a second intake air flow,respectively, in an intake of the engine; and indicating a source ofdegradation stemming from one of the engine, an intake manifold of theengine, or an exhaust system of the engine based on both the first airflow and the second air flow.

In one example, prior to spinning the engine unfueled in the forward andthe reverse direction to obtain the first intake air flow and the secondintake air flow, obtaining a set of baseline comparator data thatincludes spinning the engine unfueled in the forward and the reversedirection to obtain a first baseline intake air flow and a secondbaseline intake air flow; and wherein spinning the engine unfueled inthe forward and the reverse direction is conducted via a motor poweredby a battery.

In this way, degradation stemming from one of the engine, intakemanifold of the engine, or exhaust system of the engine, may bediagnosed, based on one test diagnostic procedure. By pinpointing wherein an engine system there is degradation, repairs may be streamlined,customer satisfaction may be improved, and release of undesiredemissions to atmosphere may be reduced.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example vehicle propulsion system.

FIG. 2 schematically shows an example vehicle system with a fuel systemand an evaporative emissions system.

FIGS. 3A-3C schematically illustrate block diagrams of a vehicle intakeand exhaust system of an engine, with potential locations fordegradation illustrated.

FIG. 4 schematically illustrates a block diagram an example autonomousdriving system.

FIGS. 5A-5B schematically shows an example H-bridge circuit which may beused to rotate a vehicle engine in a forward or reverse direction.

FIG. 6 shows a high level flowchart for indicating a presence or absenceof degradation stemming from an intake manifold, exhaust system, or anengine.

FIG. 7 shows a high level flowchart detailing steps for obtainingbaseline comparator data and for conducting an engine system diagnostic,for use in the method of FIG. 6 above.

FIG. 8 shows an example lookup table that may be used to interpretresults of the method of FIG. 6.

FIG. 9 shows an example timeline for conducting an engine systemdiagnostic, according to the methods of FIG. 6 and FIG. 7.

DETAILED DESCRIPTION

The following description relates to systems and methods for pinpointingsources of degradation stemming from either an intake manifold, exhaustsystem, or an engine of a vehicle. Such systems and methods may includespinning or rotating an engine without fuel injection, in a forward (ordefault) direction and then a reverse direction, where spinning theengine unfueled is conducted via an electric motor of a hybrid vehicle,such as the hybrid vehicle depicted at FIG. 1. More specifically, todiagnose a source of degradation in an engine system (the engine systemincluding the engine intake manifold, engine exhaust system, andengine), air flow in an intake system of the vehicle, and air flow inthe exhaust system may be monitored under a set of predeterminedconditions, and compared to a set of baseline air flow in the intakesystem and baseline air flow in the exhaust system measured under asubstantially equivalent set of predetermined conditions. Measuring airflow in the intake system may be conducted via a mass air flow (MAF)sensor positioned in the intake system, where air flow in the intakesystem may be measured under conditions where the engine is spun in theforward direction and the reverse direction. Measuring air flow in theexhaust system may be conducted via a gasoline particulate filter (GPF)differential pressure sensor under conditions where the engine is spunin the forward direction, where the GPF differential pressure sensor ispositioned in the exhaust system downstream of an exhaust manifold, asillustrated in FIG. 2. By comparing air flow in the intake system andair flow in the exhaust system to baseline measurements conducted underconditions where degradation is not present in the engine system,sources of degradation may be pinpointed as to stemming from the intakemanifold, exhaust system, or engine, as illustrated at FIGS. 3A-3C. Insome examples, the set of predetermined conditions for conductingbaseline air flow measurements on the intake system and exhaust system,and test air flow measurements on the intake system and exhaust system,may comprise an indication that the vehicle is not occupied. Thus, suchmeasurements may in some examples be carried out in an autonomousvehicle that is not occupied, where FIG. 4 depicts an example autonomousvehicle control system. For spinning the engine unfueled in the forwardand reverse directions, an H-bridge circuit may be utilized, such as theH-bridge circuit depicted at FIGS. 5A-5B. A method for pinpointing asource of degradation in an intake manifold, exhaust system, or engineis illustrated at FIG. 6. As discussed, such a method may includebaseline measurements of air flow in the intake system (under bothforward and reverse spinning of the engine) and air flow in the exhaustsystem (under forward spinning of the engine), in addition to similarmeasurements during test conditions. Accordingly, a method for obtainingsuch measurements, for use in the method depicted at FIG. 6, isillustrated at FIG. 7. To interpret the results of such a diagnostictest, the results may be analyzed via a lookup table, such as the lookuptable depicted above at FIG. 8. An example timeline for conducting suchan engine system test diagnostic procedure is illustrated at FIG. 9.

FIG. 1 illustrates an example vehicle propulsion system 100. Vehiclepropulsion system 100 includes a fuel burning engine 110 and a motor120. As a non-limiting example, engine 110 comprises an internalcombustion engine and motor 120 comprises an electric motor. Motor 120may be configured to utilize or consume a different energy source thanengine 110. For example, engine 110 may consume a liquid fuel (e.g.,gasoline) to produce an engine output while motor 120 may consumeelectrical energy to produce a motor output. As such, a vehicle withpropulsion system 100 may be referred to as a hybrid electric vehicle(HEV).

Vehicle propulsion system 100 may utilize a variety of differentoperational modes depending on operating conditions encountered by thevehicle propulsion system. Some of these modes may enable engine 110 tobe maintained in an off state (i.e., set to a deactivated state) wherecombustion of fuel at the engine is discontinued. For example, underselect operating conditions, motor 120 may propel the vehicle via drivewheel 130 as indicated by arrow 122 while engine 110 is deactivated.

During other operating conditions, engine 110 may be set to adeactivated state (as described above) while motor 120 may be operatedto charge energy storage device 150. For example, motor 120 may receivewheel torque from drive wheel 130 as indicated by arrow 122 where themotor may convert the kinetic energy of the vehicle to electrical energyfor storage at energy storage device 150 as indicated by arrow 124. Thisoperation may be referred to as regenerative braking of the vehicle.Thus, motor 120 can provide a generator function in some examples.However, in other examples, generator 160 may instead receive wheeltorque from drive wheel 130, where the generator may convert the kineticenergy of the vehicle to electrical energy for storage at energy storagedevice 150 as indicated by arrow 162.

During still other operating conditions, engine 110 may be operated bycombusting fuel received from fuel system 140 as indicated by arrow 142.For example, engine 110 may be operated to propel the vehicle via drivewheel 130 as indicated by arrow 112 while motor 120 is deactivated.During other operating conditions, both engine 110 and motor 120 mayeach be operated to propel the vehicle via drive wheel 130 as indicatedby arrows 112 and 122, respectively. A configuration where both theengine and the motor may selectively propel the vehicle may be referredto as a parallel type vehicle propulsion system. Note that in someexamples, motor 120 may propel the vehicle via a first set of drivewheels and engine 110 may propel the vehicle via a second set of drivewheels.

In other examples, vehicle propulsion system 100 may be configured as aseries type vehicle propulsion system, whereby the engine does notdirectly propel the drive wheels. Rather, engine 110 may be operated topower motor 120, which may in turn propel the vehicle via drive wheel130 as indicated by arrow 122. For example, during select operatingconditions, engine 110 may drive generator 160 as indicated by arrow116, which may in turn supply electrical energy to one or more of motor120 as indicated by arrow 114 or energy storage device 150 as indicatedby arrow 162. As another example, engine 110 may be operated to drivemotor 120 which may in turn provide a generator function to convert theengine output to electrical energy, where the electrical energy may bestored at energy storage device 150 for later use by the motor.

In still other examples, which will be discussed in detail below, motor120 may in some examples be utilized to spin or rotate the motor in anunfueled configuration. More specifically, motor 120 may rotate theengine unfueled, using power from onboard energy storage device 150,which may include a battery, capacitor, super-capacitor, etc., forexample. In a case where motor 120 is used to rotate the engineunfueled, fuel injection to engine cylinders may be prevented, and sparkmay not be provided to each of the engine cylinders. As will bediscussed in further detail below, the engine may in some examples bespun or rotated unfueled, in a forward or default direction, whereas inother examples, the engine may be spun or rotated unfueled in a reversedirection. For example, an H-bridge circuit (see FIGS. 5A-5B) may beutilized to spin the engine in a forward or reverse direction.

Fuel system 140 may include one or more fuel storage tanks 144 forstoring fuel on-board the vehicle. For example, fuel tank 144 may storeone or more liquid fuels, including but not limited to: gasoline,diesel, and alcohol fuels. In some examples, the fuel may be storedon-board the vehicle as a blend of two or more different fuels. Forexample, fuel tank 144 may be configured to store a blend of gasolineand ethanol (e.g., E10, E85, etc.) or a blend of gasoline and methanol(e.g., M10, M85, etc.), whereby these fuels or fuel blends may bedelivered to engine 110 as indicated by arrow 142. Still other suitablefuels or fuel blends may be supplied to engine 110, where they may becombusted at the engine to produce an engine output. The engine outputmay be utilized to propel the vehicle as indicated by arrow 112 or torecharge energy storage device 150 via motor 120 or generator 160.

In some examples, energy storage device 150 may be configured to storeelectrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including cabinheating and air conditioning, engine starting, headlights, cabin audioand video systems, etc. As a non-limiting example, energy storage device150 may include one or more batteries and/or capacitors.

Control system 190 may communicate with one or more of engine 110, motor120, fuel system 140, energy storage device 150, and generator 160.Control system 190 may receive sensory feedback information from one ormore of engine 110, motor 120, fuel system 140, energy storage device150, and generator 160. Further, control system 190 may send controlsignals to one or more of engine 110, motor 120, fuel system 140, energystorage device 150, and generator 160 responsive to this sensoryfeedback. Control system 190 may receive an indication of an operatorrequested output of the vehicle propulsion system from a vehicleoperator 102. For example, control system 190 may receive sensoryfeedback from pedal position sensor 194 which communicates with pedal192. Pedal 192 may refer schematically to a brake pedal and/or anaccelerator pedal. Furthermore, in some examples control system 190 maybe in communication with a remote engine start receiver 195 (ortransceiver) that receives wireless signals 106 from a key fob 104having a remote start button 105. In other examples (not shown), aremote engine start may be initiated via a cellular telephone, orsmartphone based system where a user's cellular telephone sends data toa server and the server communicates with the vehicle to start theengine.

Energy storage device 150 may periodically receive electrical energyfrom a power source 180 residing external to the vehicle (e.g., not partof the vehicle) as indicated by arrow 184. As a non-limiting example,vehicle propulsion system 100 may be configured as a plug-in hybridelectric vehicle (HEV), whereby electrical energy may be supplied toenergy storage device 150 from power source 180 via an electrical energytransmission cable 182. During a recharging operation of energy storagedevice 150 from power source 180, electrical transmission cable 182 mayelectrically couple energy storage device 150 and power source 180.While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 182 may disconnected between power source180 and energy storage device 150. Control system 190 may identifyand/or control the amount of electrical energy stored at the energystorage device, which may be referred to as the state of charge (SOC).

In other examples, electrical transmission cable 182 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 150 from power source 180. For example, energy storage device 150may receive electrical energy from power source 180 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 150 from a power source that doesnot comprise part of the vehicle. In this way, motor 120 may propel thevehicle by utilizing an energy source other than the fuel utilized byengine 110.

Fuel system 140 may periodically receive fuel from a fuel sourceresiding external to the vehicle. As a non-limiting example, vehiclepropulsion system 100 may be refueled by receiving fuel via a fueldispensing device 170 as indicated by arrow 172. In some examples, fueltank 144 may be configured to store the fuel received from fueldispensing device 170 until it is supplied to engine 110 for combustion.In some examples, control system 190 may receive an indication of thelevel of fuel stored at fuel tank 144 via a fuel level sensor. The levelof fuel stored at fuel tank 144 (e.g., as identified by the fuel levelsensor) may be communicated to the vehicle operator, for example, via afuel gauge or indication in a vehicle instrument panel 196.

The vehicle propulsion system 100 may also include an ambienttemperature/humidity sensor 198, and a roll stability control sensor,such as a lateral and/or longitudinal and/or yaw rate sensor(s) 199. Thevehicle instrument panel 196 may include indicator light(s) and/or atext-based display in which messages are displayed to an operator. Thevehicle instrument panel 196 may also include various input portions forreceiving an operator input, such as buttons, touch screens, voiceinput/recognition, etc. For example, the vehicle instrument panel 196may include a refueling button 197 which may be manually actuated orpressed by a vehicle operator to initiate refueling. For example, asdescribed in more detail below, in response to the vehicle operatoractuating refueling button 197, a fuel tank in the vehicle may bedepressurized so that refueling may be performed.

Control system 190 may be communicatively coupled to other vehicles orinfrastructures using appropriate communications technology, as is knownin the art. For example, control system 190 may be coupled to othervehicles or infrastructures via a wireless network 131, which maycomprise Wi-Fi, Bluetooth, a type of cellular service, a wireless datatransfer protocol, and so on. Control system 190 may broadcast (andreceive) information regarding vehicle data, vehicle diagnostics,traffic conditions, vehicle location information, vehicle operatingprocedures, etc., via vehicle-to-vehicle (V2V),vehicle-to-infrastructure-to-vehicle (V2I2V), and/orvehicle-to-infrastructure (V2I) technology. The communication and theinformation exchanged between vehicles can be either direct betweenvehicles, or can be multi-hop. In some examples, longer rangecommunications (e.g. WiMax) may be used in place of, or in conjunctionwith, V2V, or V2I2V, to extend the coverage area by a few miles. Instill other examples, vehicle control system 190 may be communicativelycoupled to other vehicles or infrastructures via a wireless network 131and the internet (e.g. cloud), as is commonly known in the art.

Vehicle system 100 may also include an on-board navigation system 132(for example, a Global Positioning System) that an operator of thevehicle may interact with. The navigation system 132 may include one ormore location sensors for assisting in estimating vehicle speed, vehiclealtitude, vehicle position/location, etc. This information may be usedto infer engine operating parameters, such as local barometric pressure.As discussed above, control system 190 may further be configured toreceive information via the internet or other communication networks.Information received from the GPS may be cross-referenced to informationavailable via the internet to determine local weather conditions, localvehicle regulations, etc. In one example, information received from theGPS may be utilized in conjunction with route learning methodology, suchthat routes commonly traveled by a vehicle may be learned by the vehiclecontrol system 190. In some examples, other sensors, such as lasers,radar, sonar, acoustic sensors, etc., (e.g. 133) may be additionally oralternatively utilized in conjunction with the onboard navigation systemto conduct route learning of commonly traveled routes by the vehicle.

Vehicle system 100 may also include sensors dedicated to indicating theoccupancy-state of the vehicle, for example seat load cells 107, doorsensing technology 108, and onboard cameras 109.

FIG. 2 shows a schematic depiction of a vehicle system 206. It may beunderstood that vehicle system 206 may comprise the same vehicle systemas vehicle system 100 depicted at FIG. 1. The vehicle system 206includes an engine system 208 coupled to an emissions control system 251and a fuel system 218. It may be understood that fuel system 218 maycomprise the same fuel system as fuel system 140 depicted at FIG. 1.Emission control system 251 includes a fuel vapor container or canister222 which may be used to capture and store fuel vapors. In someexamples, vehicle system 206 may be a hybrid electric vehicle system.

The engine system 208 may include an engine 110 having a plurality ofcylinders 230. While not explicitly shown, it may be understood thateach cylinder may include one or more intake valve(s) and one or moreexhaust valve(s). The engine 110 includes an engine air intake 223 andan engine exhaust 225. The engine air intake 223 includes a throttle 262in fluidic communication with engine intake manifold 244 via an intakepassage 242. The throttle 262 may comprise an electronic throttle, whichmay be controlled via the vehicle controller sending a signal to actuatethe throttle to a desired position. In such an example where thethrottle is electronic, power to control the throttle to the desiredposition may be from an onboard energy storage device (e.g. 150), suchas a battery. Further, engine air intake 223 may include an air box andfilter 215 positioned upstream of throttle 262. The engine exhaustsystem 225 includes an exhaust manifold 248 leading to an exhaustpassage 235 that routes exhaust gas to the atmosphere. The engineexhaust system 225 may include one or more emission control devices, orexhaust catalyst 270, which may be mounted in a close-coupled positionin the exhaust. The one or more emission control devices may include athree-way catalyst, lean NOx trap, diesel particulate filter, oxidationcatalyst, etc. It will be appreciated that other components may beincluded in the engine such as a variety of valves and sensors. Forexample, a barometric pressure sensor 213 may be included in the engineintake. In one example, barometric pressure sensor 213 may be a manifoldair pressure (MAP) sensor and may be coupled to the engine intakedownstream of throttle 262. Barometric pressure sensor 213 may rely onpart throttle or full or wide open throttle conditions, e.g., when anopening amount of throttle 262 is greater than a threshold, in orderaccurately determine BP. Alternatively, MAP may be inferred fromalternate engine operating conditions, such as mass air flow (MAF), asmeasured by MAF sensor 210 coupled to the intake manifold.

Engine exhaust system 225 may further include a gasoline particulatefilter (GPF) 217. GPF 217 may comprise a particulate filter, hydrocarbontrap, a catalyzed wash coat, or combination thereof. In some examples,during operation of engine 110, GPF 217 may be periodically regeneratedby operating at least one cylinder of the engine within a particularair-fuel ratio to increase a temperature of GPF 217, such that retainedhydrocarbons and soot particles may be oxidized.

In some examples, temperature sensor 226 may be positioned upstream fromthe inlet of GPF 217 and temperature sensor 229 may be positioneddownstream of GPF 217. Temperature sensors 226 and 229 may be used toassess the temperature of GPF 217 for regeneration purposes, forexample. Furthermore, pressure in the exhaust system may be assessed bypressure sensor 263. Pressure sensor 263 may be a differential pressuresensor positioned upstream and downstream of GPF 217, for example.Pressure sensor 263 may be used to determine pressure at the inlet ofGPF 217 in order to assess operating conditions for air to be introducedto the inlet of GPF 217 for regeneration. Furthermore, in some examples,soot sensor 268 may be positioned downstream of GPF 217, to assess thelevel of soot that is released from GPF 217. Soot sensor 268 may be usedto diagnose operation of GPF 217, among other functions.

Fuel system 218 may include a fuel tank 220 coupled to a fuel pumpsystem 221. It may be understood that fuel tank 220 may comprise thesame fuel tank as fuel tank 144 depicted above at FIG. 1. The fuel pumpsystem 221 may include one or more pumps for pressurizing fuel deliveredto the injectors of engine 110, such as the example injector 266 shown.While only a single injector 266 is shown, additional injectors areprovided for each cylinder. It will be appreciated that fuel system 218may be a return-less fuel system, a return fuel system, or various othertypes of fuel system. Fuel tank 220 may hold a plurality of fuel blends,including fuel with a range of alcohol concentrations, such as variousgasoline-ethanol blends, including E10, E85, gasoline, etc., andcombinations thereof. A fuel level sensor 234 located in fuel tank 220may provide an indication of the fuel level (“Fuel Level Input”) tocontroller 212. As depicted, fuel level sensor 234 may comprise a floatconnected to a variable resistor. Alternatively, other types of fuellevel sensors may be used.

Vapors generated in fuel system 218 may be routed to an evaporativeemissions control system 251 which includes a fuel vapor canister 222via vapor recovery line 231, before being purged to the engine airintake 223. Vapor recovery line 231 may be coupled to fuel tank 220 viaone or more conduits and may include one or more valves for isolatingthe fuel tank during certain conditions. For example, vapor recoveryline 231 may be coupled to fuel tank 220 via one or more or acombination of conduits 271, 273, and 275.

Further, in some examples, one or more fuel tank vent valves may bepositioned in conduits 271, 273, or 275. Among other functions, fueltank vent valves may allow a fuel vapor canister of the emissionscontrol system to be maintained at a low pressure or vacuum withoutincreasing the fuel evaporation rate from the tank (which wouldotherwise occur if the fuel tank pressure were lowered). For example,conduit 271 may include a grade vent valve (GVV) 287, conduit 273 mayinclude a fill limit venting valve (FLVV) 285, and conduit 275 mayinclude a grade vent valve (GVV) 283. Further, in some examples,recovery line 231 may be coupled to a fuel filler system 219. In someexamples, fuel filler system may include a fuel cap 205 for sealing offthe fuel filler system from the atmosphere. Refueling system 219 iscoupled to fuel tank 220 via a fuel filler pipe or neck 211.

Further, refueling system 219 may include refueling lock 245. In someexamples, refueling lock 245 may be a fuel cap locking mechanism. Thefuel cap locking mechanism may be configured to automatically lock thefuel cap in a closed position so that the fuel cap cannot be opened. Forexample, the fuel cap 205 may remain locked via refueling lock 245 whilepressure or vacuum in the fuel tank is greater than a threshold. Inresponse to a refuel request, e.g., a vehicle operator initiatedrequest, the fuel tank may be depressurized and the fuel cap unlockedafter the pressure or vacuum in the fuel tank falls below a threshold. Afuel cap locking mechanism may be a latch or clutch, which, whenengaged, prevents the removal of the fuel cap. The latch or clutch maybe electrically locked, for example, by a solenoid, or may bemechanically locked, for example, by a pressure diaphragm.

In some examples, refueling lock 245 may be a filler pipe valve locatedat a mouth of fuel filler pipe 211. In such examples, refueling lock 245may not prevent the removal of fuel cap 205. Rather, refueling lock 245may prevent the insertion of a refueling pump into fuel filler pipe 211.The filler pipe valve may be electrically locked, for example by asolenoid, or mechanically locked, for example by a pressure diaphragm.

In some examples, refueling lock 245 may be a refueling door lock, suchas a latch or a clutch which locks a refueling door located in a bodypanel of the vehicle. The refueling door lock may be electricallylocked, for example by a solenoid, or mechanically locked, for exampleby a pressure diaphragm.

In examples where refueling lock 245 is locked using an electricalmechanism, refueling lock 245 may be unlocked by commands fromcontroller 212, for example, when a fuel tank pressure decreases below apressure threshold. In examples where refueling lock 245 is locked usinga mechanical mechanism, refueling lock 245 may be unlocked via apressure gradient, for example, when a fuel tank pressure decreases toatmospheric pressure.

Emissions control system 251 may include one or more emissions controldevices, such as one or more fuel vapor canisters 222 filled with anappropriate adsorbent 286 b, the canisters are configured to temporarilytrap fuel vapors (including vaporized hydrocarbons) during fuel tankrefilling operations and “running loss” (that is, fuel vaporized duringvehicle operation). In one example, the adsorbent 286 b used isactivated charcoal. Emissions control system 251 may further include acanister ventilation path or vent line 227 which may route gases out ofthe canister 222 to the atmosphere when storing, or trapping, fuelvapors from fuel system 218.

Canister 222 may include a buffer 222 a (or buffer region), each of thecanister and the buffer comprising the adsorbent. As shown, the volumeof buffer 222 a may be smaller than (e.g., a fraction of) the volume ofcanister 222. The adsorbent 286 a in the buffer 222 a may be same as, ordifferent from, the adsorbent in the canister (e.g., both may includecharcoal). Buffer 222 a may be positioned within canister 222 such thatduring canister loading, fuel tank vapors are first adsorbed within thebuffer, and then when the buffer is saturated, further fuel tank vaporsare adsorbed in the canister. In comparison, during canister purging,fuel vapors are first desorbed from the canister (e.g., to a thresholdamount) before being desorbed from the buffer. In other words, loadingand unloading of the buffer is not linear with the loading and unloadingof the canister. As such, the effect of the canister buffer is to dampenany fuel vapor spikes flowing from the fuel tank to the canister,thereby reducing the possibility of any fuel vapor spikes going to theengine. One or more temperature sensors 232 may be coupled to and/orwithin canister 222. As fuel vapor is adsorbed by the adsorbent in thecanister, heat is generated (heat of adsorption). Likewise, as fuelvapor is desorbed by the adsorbent in the canister, heat is consumed. Inthis way, the adsorption and desorption of fuel vapor by the canistermay be monitored and estimated based on temperature changes within thecanister.

Vent line 227 may also allow fresh air to be drawn into canister 222when purging stored fuel vapors from fuel system 218 to engine intake223 via purge line 228 and purge valve 261. For example, purge valve 261may be normally closed but may be opened during certain conditions sothat vacuum from engine intake manifold 244 is provided to the fuelvapor canister for purging. In some examples, vent line 227 may includean air filter 259 disposed therein upstream of a canister 222.

In some examples, the flow of air and vapors between canister 222 andthe atmosphere may be regulated by a canister vent valve 297 coupledwithin vent line 227. When included, the canister vent valve 297 may bea normally open valve, so that fuel tank isolation valve 252 (FTIV) maycontrol venting of fuel tank 220 with the atmosphere. FTIV 252 may bepositioned between the fuel tank and the fuel vapor canister 222 withinconduit 278. FTIV 252 may be a normally closed valve, that when opened,allows for the venting of fuel vapors from fuel tank 220 to fuel vaporcanister 222. Fuel vapors may then be vented to atmosphere, or purged toengine intake system 223 via canister purge valve 261. As will bediscussed in detail below, in some example the FTIV may not be included,whereas in other examples, an FTIV may be included.

Fuel system 218 may be operated by controller 212 in a plurality ofmodes by selective adjustment of the various valves and solenoids. Itmay be understood that control system 214 may comprise the same controlsystem as control system 190 depicted above at FIG. 1. For example, thefuel system may be operated in a fuel vapor storage mode (e.g., during afuel tank refueling operation and with the engine not combusting air andfuel), wherein the controller 212 may open isolation valve 252 (whenincluded) while closing canister purge valve (CPV) 261 to directrefueling vapors into canister 222 while preventing fuel vapors frombeing directed into the intake manifold.

As another example, the fuel system may be operated in a refueling mode(e.g., when fuel tank refueling is requested by a vehicle operator),wherein the controller 212 may open isolation valve 252 (when included),while maintaining canister purge valve 261 closed, to depressurize thefuel tank before allowing enabling fuel to be added therein. As such,isolation valve 252 (when included) may be kept open during therefueling operation to allow refueling vapors to be stored in thecanister. After refueling is completed, the isolation valve may beclosed.

As yet another example, the fuel system may be operated in a canisterpurging mode (e.g., after an emission control device light-offtemperature has been attained and with the engine combusting air andfuel), wherein the controller 212 may open canister purge valve 261while closing isolation valve 252 (when included). Herein, the vacuumgenerated by the intake manifold of the operating engine may be used todraw fresh air through vent 227 and through fuel vapor canister 222 topurge the stored fuel vapors into intake manifold 244. In this mode, thepurged fuel vapors from the canister are combusted in the engine. Thepurging may be continued until the stored fuel vapor amount in thecanister is below a threshold.

Controller 212 may comprise a portion of a control system 214. In someexamples, control system 214 may be the same as control system 190,illustrated in FIG. 1. Control system 214 is shown receiving informationfrom a plurality of sensors 216 (various examples of which are describedherein) and sending control signals to a plurality of actuators 281(various examples of which are described herein). As one example,sensors 216 may include exhaust gas sensor 237 located upstream of theemission control device 270, temperature sensor 233, pressure sensor291, pressure sensor 282, canister temperature sensor 232, MAF sensor210, and pressure sensor 263. Other sensors such as pressure,temperature, air/fuel ratio, and composition sensors may be coupled tovarious locations in the vehicle system 206. As another example, theactuators may include throttle 262, fuel tank isolation valve 252,canister purge valve 261, and canister vent valve 297. The controllermay receive input data from the various sensors, process the input data,and trigger the actuators in response to the processed input data basedon instruction or code programmed therein corresponding to one or moreroutines. Example control routines are described herein with regard toFIGS. 6-7.

In some examples, the controller may be placed in a reduced power modeor sleep mode, wherein the controller maintains essential functionsonly, and operates with a lower battery consumption than in acorresponding awake mode. For example, the controller may be placed in asleep mode following a vehicle-off event in order to perform adiagnostic routine at a duration after the vehicle-off event. Thecontroller may have a wake input that allows the controller to bereturned to an awake mode based on an input received from one or moresensors. For example, the opening of a vehicle door may trigger a returnto an awake mode, or a remote start event may trigger a return to anawake mode. In other examples, particularly with regard to the methodsdepicted in FIGS. 6-7, the controller may be required to be awake inorder to conduct such methods. For example, a wakeup capability mayenable a circuit to wake the controller in order to obtain baselinecomparator data, or to conduct an engine system diagnostic, as will bediscussed in further detail below.

Undesired evaporative emissions detection routines may be intermittentlyperformed by controller 212 on fuel system 218 and/or evaporativeemissions system 251 to confirm that undesired evaporative emissions arenot present in the fuel system and/or evaporative emissions system. Assuch, evaporative emissions detection routines may be performed whilethe engine is off (engine-off test) using engine-off natural vacuum(EONV) generated due to a change in temperature and pressure at the fueltank following engine shutdown and/or with vacuum supplemented from avacuum pump. Alternatively, evaporative emissions detection routines maybe performed while the engine is running by operating a vacuum pumpand/or using engine intake manifold vacuum. In some configurations, acanister vent valve (CVV) 297 may be coupled within vent line 227. CVV297 may function to adjust a flow of air and vapors between canister 222and the atmosphere. The CVV may also be used for diagnostic routines.When included, the CVV may be opened during fuel vapor storingoperations (for example, during fuel tank refueling and while the engineis not running) so that air, stripped of fuel vapor after having passedthrough the canister, can be pushed out to the atmosphere. Likewise,during purging operations (for example, during canister regeneration andwhile the engine is running), the CVV may be opened to allow a flow offresh air to strip the fuel vapors stored in the canister. In someexamples, CVV 297 may be a solenoid valve wherein opening or closing ofthe valve is performed via actuation of a canister vent solenoid. Inparticular, the canister vent valve may be an open that is closed uponactuation of the canister vent solenoid. In some examples, CVV 297 maybe configured as a latchable solenoid valve. In other words, when thevalve is placed in a closed configuration, it latches closed withoutrequiring additional current or voltage. For example, the valve may beclosed with a 100 ms pulse, and then opened at a later time point withanother 100 ms pulse. In this way, the amount of battery power requiredto maintain the CVV closed is reduced.

In another example, an engine system diagnostic may be conducted inorder to determine whether a source of degradation stems from an intakemanifold of the engine, an exhaust system of the engine, or the engineitself. Such an example will be discussed in detail below with regard tothe methods depicted at FIGS. 6-7. Discussed herein, degradation of theintake manifold may refer to a puncture, crack, degraded gasket, loosecoupling, or air leak in the intake manifold. Degradation of the exhaustsystem may similarly refer to a puncture, crack, degraded gasket, loosecoupling, or exhaust leak in the exhaust system. It may be understoodthat degradation of the exhaust system may refer to the engine systemupstream of the GPF (e.g. 217) or differential pressure sensor (e.g.263), and downstream of the engine (e.g. 110). Finally, degradation ofthe engine may refer to intake/exhaust valves that are not sealingproperly, undesired camshaft timing, compression issues, or any otherengine-specific issues which may result in the engine not pumping aseffectively as expected or demanded.

Turning now to FIGS. 3A-3C, they illustrate examples of sources ofdegradation stemming from the intake manifold, exhaust system, orengine, respectively. Accordingly, FIGS. 3A-3C illustrate simplifiedblock diagrams of the engine system comprising MAF sensor 210, intakemanifold 244, engine 110, exhaust system 225, GPF 217, and differentialpressure sensor 263. As such, FIGS. 3A-3C represent simplified blockdiagrams of the engine system depicted above at FIG. 2. In each of FIGS.3A-3C, as will be elaborated below, a source of degradation isillustrated, denoted as 310 a, 310 b, and 310 c.

Turning now to FIG. 3A, it shows an example where a source ofdegradation 310 a is stemming from intake manifold 244. In such anexample, the source of degradation 310 a is not directly observable viaMAF sensor 210, as the source of degradation is downstream of MAF sensor210. However, while the engine is in operation, unmetered air may bedrawn into the engine via the source of degradation. Thus, it may beunderstood that additional air (in addition to that drawn through theintake passage (e.g. 242) may be drawn into the engine, and accordinglypressure in the exhaust system may be greater than expected, asmonitored by the differential pressure sensor 263. Accordingly, as willbe discussed in further detail below with regard to FIGS. 6-9, it may bepossible in such an example to diagnose the source of degradation 310 ain the intake manifold 244 if air flow as indicated via MAF sensor 210is substantially equivalent to an expected air flow under a set ofpredetermined conditions, but where exhaust flow (e.g. pressure in theexhaust system) as indicated by differential pressure sensor 263, isgreater than an expected exhaust flow under the same (or substantiallyequivalent) set of predetermined conditions. Such an example may involvespinning the engine unfueled in a forward direction to obtain the MAFsensor data and the differential pressure sensor data. In other words,the exhaust flow as indicated by differential pressure sensor 263 may begreater than expected due to the unmetered air being drawn into theengine and through the exhaust system via the source of degradation 310a when the engine is spun unfueled in the forward direction.

In another example, it may additionally or alternatively be possible todiagnose a source of degradation in the intake manifold by firstspinning the engine unfueled in the forward or default direction andmonitoring air flow in the intake system via the MAF sensor, and thenspinning the engine unfueled in the reverse direction and againmonitoring air flow in the intake system via the MAF sensor. In such anexample, if there is a source of degradation 310 a in the intakemanifold, then MAF sensor data recorded while spinning the engineunfueled in the forward direction may be greater than the MAF sensordata recorded while spinning the engine unfueled in reverse, as less airflow may reach the MAF sensor due to the source of degradation 310 a,when the engine is spun unfueled in reverse. In other words, whenspinning the engine unfueled in the forward direction, the MAF sensor210 may not detect unmetered air which may be drawn into the engine viathe source of degradation 310 a. However, when the engine is spun inreverse, the air flow generated in the intake by spinning the engine inreverse may at least partially exit through the source of degradation310 a, thus resulting in less air flow as monitored via the MAF sensor,than expected (for example compared to baseline measurements in theabsence of degradation).

Turning now to FIG. 3B, it shows an example where a source ofdegradation 310 b is stemming from the exhaust system 225. In such anexample, the source of degradation is not directly observable via MAFsensor 210, or differential pressure sensor 263, alone. However, whilethe engine is in operation, for example being spun unfueled in theforward direction, exhaust flow may be pushed or forced to atmospherevia the source of degradation 310 b, resulting in an overall lessexhaust flow as monitored via the differential pressure sensor 263.Accordingly, as will be discussed in further detail below with regard toFIGS. 6-9, it may be possible to diagnose a source of degradation in theexhaust system 225 if mass air flow as indicated via MAF sensor 210 issubstantially equivalent to an expected mass air flow under a set ofpredetermined conditions, but where exhaust flow (e.g. pressure in theexhaust system) as indicated by differential pressure sensor 263, isless than an expected exhaust flow under the same (or substantiallyequivalent) set of predetermined conditions.

Turning now to FIG. 3C, it shows an example where a source ofdegradation 310 c is stemming from engine 110. As mentioned above, asource of degradation 310 c stemming from the engine 110 may compriseintake/exhaust valves that are not sealing properly, undesired camshafttiming, compression issues, or any other engine-specific issues whichmay result in the engine not pumping as effectively as expected ordemanded. In such an example, MAF sensor 210 may not directly be used toinfer a source of degradation stemming from the engine, and similarlydifferential pressure sensor 263 may not directly be used to infer sucha source of degradation. However, an engine with a source of degradationmay not pump as efficiently as expected, and as such, an amount of airdrawn into the intake passage (e.g. 242) may be lower than expectedunder a set of predetermined conditions. Similarly, because less airoverall was drawn into the engine via the intake passage, then lessexhaust flow may occur as a result. Accordingly, as will be discussed infurther detail below with regard to FIGS. 6-9, it may be possible todiagnose a source of degradation stemming from engine 110 if intake massair flow as indicated by MAF sensor 210 is substantially equivalent toexhaust flow as indicated by differential pressure sensor 263, but whereboth intake mass air flow and exhaust flow are lower than expected undera set of predetermined conditions where the engine is spun unfueled inthe forward direction.

In another example, it may be possible to diagnose the source ofdegradation stemming from engine 110 if air flow in the intake asmonitored via the MAF sensor when the engine is spun unfueled in theforward direction is substantially equivalent to air flow in the intakeas monitored via the MAF sensor when the engine is spun unfueled in thereverse direction, but where the air flow in response to the enginebeing spun in both the forward and reverse directions is lower thanexpected (e.g. lower than baseline comparator data).

The set of predetermined conditions, as discussed above with regard toFIGS. 3A-3C may include engine speed at a predetermined speed (e.g.predetermined RPM), a position of a throttle (e.g. 262) at apredetermined angle or level of opening, the engine being rotated orspun unfueled via power from an onboard energy storage device (e.g.150), etc. Furthermore, as discussed above, “expected” amounts of airflow in the intake manifold and exhaust system may comprise air flowamounts that have been previously established during conditions where nosource of degradation is indicated, under conditions of spinning theengine unfueled in both the forward and reverse directions. In otherwords, as will be discussed in further detail below, expected amounts ofair flow in the intake (under forward and reverse engine spinning) andexhaust system (under forward engine spinning) may comprise baseline airflow in the intake manifold and baseline air flow in the exhaust system,under a substantially equivalent set of predetermined conditions as thatdiscussed above with regard to FIGS. 3A-3C.

As discussed, systems and methods for diagnosing the engine system mayinclude rotating or spinning the engine unfueled to establish baseline,or expected, air flow in the intake manifold and exhaust system underconditions where degradation is not already indicated. Furthermore, whenconducting the engine system diagnostic comprising comparing valuesobtained via the MAF sensor 210 and differential pressure sensor 263,the systems and methods may similarly include rotating or spinning theengine unfueled. Accordingly, to avoid customer dissatisfaction due tothe engine being spun without being fueled, such an engine systemdiagnostic may execute under conditions where a vehicle operator andpassengers are not indicated to be in the vehicle. Examples may includea remote start event when the vehicle is not occupied, a “wake-up” ofthe vehicle controller some predetermined duration after a key-off eventwhere the vehicle is not occupied, immediately after a key-off where thecontroller is maintained awake to conduct the diagnostic, etc. In stillanother example, the engine system diagnostic may be conducted in anautonomous vehicle in which the vehicle is indicated to be unoccupied.In each of the above-mentioned examples, vehicle occupancy may beindicated by one or more of seat load cells (e.g. 107, door sensingtechnology (e.g. 108), and/or onboard camera(s) (e.g. 109).

As the engine system diagnostic discussed above may be conducted in avehicle configured as an autonomous vehicle, an example autonomousdriving system is discussed below with regard to FIG. 4. FIG. 4 is ablock diagram of an example autonomous driving system 400 that mayoperate the vehicle system 100, described above at FIG. 1. Herein, thevehicle system 100 will be referred to simply as a “vehicle”. Theautonomous driving system 400, as shown, includes a user interfacedevice 410, a navigation system 415, at least one autonomous drivingsensor 420, and an autonomous mode controller 425. It may be understoodthat the onboard navigation system 415 may be the same as the onboardnavigation system 132 depicted above at FIG. 1.

The user interface device 410 may be configured to present informationto vehicle occupants, under conditions wherein a vehicle occupant may bepresent. However, it may be understood that the vehicle may be operatedautonomously in the absence of vehicle occupants, under certainconditions. The presented information may include audible information orvisual information. Moreover, the user interface device 410 may beconfigured to receive user inputs. Thus, the user interface device 410may be located in the passenger compartment (not shown) of the vehicle.In some possible approaches, the user interface device 410 may include atouch-sensitive display screen.

The navigation system 415 may be configured to determine a currentlocation of the vehicle using, for example, a Global Positioning System(GPS) receiver configured to triangulate the position of the vehiclerelative to satellites or terrestrial based transmitter towers. Thenavigation system 415 may be further configured to develop routes fromthe current location to a selected destination, as well as display a mapand present driving directions to the selected destination via, forexample, the user interface device 410.

The autonomous driving sensors 420 may include any number of devicesconfigured to generate signals that help navigate the vehicle. Examplesof autonomous driving sensors 420 may include a radar sensor, a lidarsensor, a vision sensor (e.g. a camera), vehicle to vehicleinfrastructure networks, or the like. The autonomous driving sensors 420may enable the vehicle to “see” the roadway and vehicle surroundings,and/or negotiate various obstacles while the vehicle 100 is operating inautonomous mode. The autonomous driving sensors 420 may be configured tooutput sensor signals to, for example, the autonomous mode controller425.

The autonomous mode controller 425 may be configured to control one ormore subsystems 430 while the vehicle is operating in the autonomousmode. Examples of subsystems 430 that may be controlled by theautonomous mode controller 425 may include a brake subsystem, asuspension subsystem, a steering subsystem, and a powertrain subsystem.The autonomous mode controller 425 may control any one or more of thesesubsystems 430 by outputting signals to control units associated withsubsystems 430. In one example, the brake subsystem may comprise ananti-lock braking subsystem, configured to apply a braking force to oneor more of wheels (e.g. 135). Discussed herein, applying the brakingforce to one or more of the vehicle wheels may be referred to asactivating the brakes. To autonomously control the vehicle, theautonomous mode controller 425 may output appropriate commands to thesubsystems 430. The commands may cause the subsystems to operate inaccordance with the driving characteristics associated with the selecteddriving mode. For example, driving characteristics may include howaggressively the vehicle accelerates and decelerates, how much space thevehicle leaves behind a front vehicle, how frequently the autonomousvehicle changes lanes, etc.

FIGS. 5A and 5B show an example circuit 500 that may be used forreversing a spin orientation of an electric motor. Circuit 500schematically depicts an H-Bridge circuit that may be used to run amotor 510 in a first (forward) direction and alternately in a second(reverse) direction. Circuit 500 comprises a first (LO) side 520 and asecond (HI) side 530. Side 520 includes transistors 521 and 522, whileside 530 includes transistors 531 and 532. Circuit 500 further includesa power source 540.

In FIG. 5A, transistors 521 and 532 are activated (energized), whiletransistors 522 and 531 are off. In this configuration, the left lead551 of motor 510 is connected to power source 540, and the right lead552 of motor 510 is connected to ground. In this way, motor 500 may runin a forward (or default) direction. When operating the engine in aforward direction via the motor, the engine may be in a cranking modefor initial combustion commencement. Additionally and/or alternatively,when operating the engine in a forward direction via the motor, theengine (and motor or another motor) may be in a drive mode to drive thevehicle. It may be understood that in some examples, the engine may bespun in the forward (e.g. default) direction under conditions where thevehicle is stationary and it is desired only for the engine to be spunor rotated in the forward direction, without combustion.

In FIG. 5B, transistors 522 and 531 are activated (energized), whiletransistors 521 and 532 are off. In this configuration, the right lead552 of motor 510 is connected to power source 540, and the left lead 551of motor 510 is connected to ground. In this way, motor 510 may run in areverse direction.

Turning now to FIG. 6, a high level example method 600 for conducting anengine system diagnostic, is shown. More specifically, method 600 may beused to diagnose the presence or absence of degradation stemming from anintake manifold, exhaust system, or engine of a vehicle, by comparingair flow in the intake system and air flow in the exhaust system under aset of predetermined conditions to a baseline air flow in the intakesystem and a baseline air flow in the exhaust system (under asubstantially equivalent set of predetermined conditions). In this way,sources of degradation may be pinpointed as to being either in theintake manifold, exhaust system, or engine compartment. By pinpointing asource of degradation, repair procedures may be streamlined, andoperational issues related to the engine system may be diagnosed rapidlyand precisely, which may result in an increased lifespan of enginesystem componentry.

Method 600 will be described with reference to the systems describedherein and shown in FIGS. 1-5B, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 600 may be carried out by acontroller, such as controller 212 in FIG. 2, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 600 and the rest of the methodsincluded herein may be executed by the controller based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1-4. The controller may employengine system actuators, such as motor (e.g. 120), throttle (e.g. 262),canister purge valve (e.g. 261), etc., according to the method below.

Method 600 begins at 605 and may include indicating whether conditionsare met for obtaining baseline comparator data for the engine systemdiagnostic, where baseline comparator data includes measurements of airflow in the intake system under conditions of forward and reverse enginespinning, as well as measurements of air flow in the exhaust systemunder conditions of forward, and in some examples, reverse enginespinning. Conditions being met for obtaining baseline comparator datamay include an indication that the vehicle is not occupied. As discussedabove, seat load cells, onboard camera(s), and/or door sensingtechnology may be utilized to ensure that the vehicle is not occupied.Baseline comparator data may be thus obtained responsive to a remotestart event, or a wakeup of the controller a predetermined durationafter a key-off event, or in a case where the vehicle comprises anautonomous vehicle that is unoccupied and not in motion. Morespecifically, if the vehicle is in operation, for example if the vehicleis being propelled via either a motor (e.g. 120), engine (e.g. 110), orsome combination thereof, conditions may not be indicated to be met forobtaining baseline comparator data for the engine system diagnostic.Still further, conditions being indicated to be met at 605 may includean indication that a source of degradation is not already indicated tobe present in the intake manifold, exhaust system, or engine of thevehicle. For example, baseline comparator data may be obtained initiallyon a new engine system, where it is established that no part of theengine system is degraded. Subsequently, in the absence of an indicationotherwise (e.g. sudden lean air/fuel ratio), baseline data may beperiodically acquired via the controller on the non-degraded enginesystem. In the case of a sudden air/fuel ratio shift, then the baselinecomparator data to be utilized for conducting the engine system testdiagnostic (discussed below) may comprise the most recent baselinecomparator data prior to the air/fuel ratio shift.

Furthermore, conditions being met at 605 for obtaining baselinecomparator data may include an indication that baseline comparator datahas not been obtained for a predetermined duration of time since a priorbaseline comparator data measurement. In some examples, such apredetermined duration of time may comprise 1 day, greater than 1 daybut less than 2 days, greater than 2 days but less than 5 days, greaterthan 5 days but less than 10 days, greater than 10 days, etc. If, at605, it is indicated that conditions are indicated to be met forobtaining baseline comparator data, method 600 may proceed to 610, wherebaseline comparator data may be obtained according to method 700depicted at FIG. 7.

Alternatively, if conditions are not indicated to be met at 605 forobtaining baseline comparator data, method 600 may proceed to 615, andmay include indicating whether conditions are met for conducting theengine system diagnostic. Conditions being met for conducting the enginesystem diagnostic may similarly include an indication that the vehicleis not occupied, which may include a remote start event, a controllerwake-up a predetermined duration after a key-off event, or an unoccupiedautonomous vehicle. Furthermore, conditions being met for conducting theengine system diagnostic at 615 may include an indication that baselinecomparator data has been obtained within a threshold duration of theengine system diagnostic that is desired to be conducted at 615. In someexamples, the threshold duration since baseline comparator data has beenobtained may comprise 1 day or less, greater than 1 day but less than 2days, greater than 2 days but less than three days, etc. Still further,conditions being met for conducting the engine system diagnostic at 615may include an indication that the air intake system filter (e.g. 215)has not been replaced since baseline comparator data has been obtained,and may further include an indication that the GPF (e.g. 217), whereincluded, has not been regenerated since the baseline comparator datawas obtained. Another example of conditions being met for conducting theengine system diagnostic includes an indication that a source ofdegradation is not already indicated to be present in the intakemanifold, exhaust system, or engine of the vehicle.

In still further examples, conditions being met for conducting theengine system diagnostic may include an indication of a disturbance toan air-fuel ratio, as monitored via an exhaust gas sensor (e.g. 237).For example, if during a drive cycle where the engine is operating (e.g.combusting air and fuel), it is indicated that the engine system isrunning lean (or rich), one possibility may be that there is a source ofdegradation stemming from either the intake manifold, exhaust system, orengine. An indication the engine is operating too lean may be provided,for example, from a long term correction in combustion air/fuel ratiofor a lean air/fuel bias. Accordingly, if the engine system indicates anunexpected air-fuel ratio, then such an indication may be stored at thecontroller. Such an indication being stored at the controller maytrigger the engine system diagnostic to be conducted, provided that allconditions are met for conducting the engine system diagnostic at step615 of method 600.

If, at step 615, it is indicated that conditions are not met forconducting the engine system diagnostic, method 600 may proceed to 620,and may include maintaining current vehicle operating parameters. Forexample, if the vehicle is not in operation, where the engine is off(not combusting air and fuel), and where the motor is not being utilizedto propel the vehicle, then such conditions may be maintained.Alternatively, if the vehicle is in operation, then current vehicleoperating parameters may be maintained. In an example case where anair-fuel ratio disturbance was indicated, and thus an engine systemdiagnostic is desired, but where conditions are not indicated to be metat 615, such an indication may be stored at the controller such that theengine system diagnostic may be triggered to be conducted responsive toconditions being met for conducting the engine system diagnostic. In afurther example where one of the conditions not being indicated to bemet at 615 includes the absence of appropriate baseline comparator data(e.g. baseline comparator data obtained greater than the thresholdduration prior to execution of the engine system diagnostic, orconditions where the intake air filter (e.g. 215) was replaced or theGPF, where included, was regenerated subsequent to obtaining baselinecomparator data), the method may include setting flag at the controllerand illuminating a malfunction indicator light on a vehicle dash. Suchan indication may alert the vehicle operator of a need to service thevehicle, for a potential source of degradation stemming from the intakemanifold, exhaust system, or engine compartment, for example, because inthe absence of appropriate baseline comparator data, the engine systemdiagnostic may not be conducted.

To prevent such a situation, in some examples, the vehicle controllermay prevent GPF regeneration until an engine system diagnostic has beenconducted, responsive to obtaining baseline comparator data. However,the controller may rely on pressure measurements as indicated via thedifferential pressure sensor (e.g. 263) to determine whether it isdesirable to regenerate the GPF at the expense of an engine systemdiagnostic, or whether the GPF regeneration may be prevented until theengine system diagnostic has been conducted. For example, if, duringengine operation, a threshold pressure differential (e.g. within 5-10%or less of a pressure differential indicating saturation of the GPF) isobtained via the differential pressure sensor (e.g. 263) correspondingto the GPF, then it may be determined that the GPF may be regenerated,even though such an event may result in the engine system diagnostic notbeing able to be conducted until subsequent baseline comparator data isobtained.

In a case where the GPF is regenerated subsequent to obtaining baselinecomparator data, such that new baseline comparator data may be obtained,a flag may be set at the controller indicating that the GPF wasregenerated subsequent to baseline comparator data being obtained, suchthat new baseline comparator data may be obtained at the next availableopportunity (e.g. when conditions are met for obtaining baselinecomparator data, as discussed above).

A similar situation may arise if the intake air filter (e.g. 215) isreplaced subsequent to baseline comparator data being obtained. Forexample, a flag may be set at the controller under such circumstances,instructing the vehicle controller to subsequently obtain baselinecomparator data at the next opportunity where conditions are indicatedto be met for obtaining baseline comparator data.

Returning to step 615 of method 600, if conditions are indicated to bemet for conducting the engine system diagnostic, method 600 may proceedto 625, and may include conducting the engine system diagnosticaccording to FIG. 7. It may be understood that both obtaining baselinecomparator data and conducting the engine system diagnostic may comprisesubstantially equivalent methodology, encompassed by method 700.

Accordingly, turning now to FIG. 7, a high level example method 700 forobtaining baseline comparator data and/or conducting the engine systemdiagnostic, is shown. More specifically, method 700 may be utilized toobtain baseline comparator data that may be used in conjunction withmethod 600 depicted at FIG. 6, in order to conduct the engine systemdiagnostic that relies on the baseline comparator data (and whereconducting the engine system diagnostic also includes running method700). In this way, a source of degradation may be pinpointed as tostemming from an intake manifold, an exhaust system, or an engine of avehicle. Discussed herein, baseline comparator data may includemeasurements of air flow in the intake as measured by the MAF sensor(e.g. 210) with the engine being spun unfueled in forward direction, andthen the reverse direction, and measurements of air flow in the exhaustsystem as measured by the differential pressure sensor (e.g. 263) withthe engine being spun unfueled in the forward direction, and in someexamples, with the engine being spun unfueled in the reverse direction.Similarly, “conducting the engine system diagnostic” may also includeobtaining measurements of air flow in the intake where the engine isspun unfueled in the forward and then reverse direction, andmeasurements of air flow in the exhaust system where the engine is spununfueled in the forward direction, and in some examples, with the enginebeing spun unfueled in the reverse direction. It may be understood that,while the engine is being spun in the forward direction, both themeasurements of air flow in the intake and measurements of air flow inthe exhaust system, may be determined, and vice versa.

Method 700 will be described with reference to the systems describedherein and shown in FIGS. 1-5B, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 700 may be carried out by acontroller, such as controller 212 in FIG. 2, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 700 and the rest of the methodsincluded herein may be executed by the controller based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1-4. The controller may employengine system actuators, such as motor (e.g. 120), throttle (e.g. 262),canister purge valve (e.g. 261), etc., according to the method below.

As discussed, method 700 may be conducted to obtain baseline comparatordata, and subsequently, method 700 may be utilized to conduct the enginesystem diagnostic, where the engine system diagnostic utilizes thebaseline comparator data to determine whether there is degradationstemming from the intake manifold, exhaust system, or engine of thevehicle. Thus, method 700 will be described initially as being utilizedfor obtaining baseline comparator data. Subsequently, it will bediscussed as to how method 700 may be used to conduct the engine systemdiagnostic.

Method 700 begins at 705 and may include controlling a throttle (e.g.262) to a predetermined throttle position. As discussed above, such athrottle may comprise an electronic throttle, which may be actuated toopen or close via the vehicle controller, using power supplied from anonboard energy storage device (e.g. 150), which may include a battery,for example. The predetermined throttle position may comprise a positionthat is more open than a closed position, for example, to allow intakeair to be drawn into the engine via the intake manifold when the engineis spun in the forward direction, and/or to allow for air to be pushedto atmosphere via the intake when the engine is spun in the reversedirection (e.g. atmospheric air may be drawn into the engine via theexhaust system, and pushed to atmosphere via the intake manifold andintake of the engine). For example, the throttle may be actuated tofully open, or to some fraction (e.g. 75%, 60%, 50%, 40%, 30%, 20%,etc.) of fully open.

Responsive to controlling the throttle to the predetermined throttleposition, method 700 may proceed to 710. At 710, method 700 may includerotating or spinning the engine unfueled for a predetermined duration ata predetermined speed (e.g. predetermined RPM). The predeterminedduration may comprise a duration whereby robust measurements of air flowmay be obtained via the MAF sensor (e.g. 210), and via the differentialpressure sensor (e.g. 263). Rotating the engine unfueled may compriserotating the engine in the same direction as when the engine is operatedto combust air and fuel. In other words, rotating the engine unfueledmay comprise rotating the engine in a forward or default direction.Rotating the engine unfueled in the forward direction may compriserouting air flow through the intake of the engine, intake manifold ofthe engine, the engine, and the exhaust system of the engine, in thatorder. Rotating the engine unfueled may further comprise rotating theengine via the motor (e.g. 120), where the motor may be powered via theonboard energy storage device (e.g. 150), such as a battery. The speedof the engine may be further controlled via the motor, to thepredetermined speed. The predetermined engine speed may comprise a speedat which robust measurements of air flow may be obtained via the MAFsensor (e.g. 210), and via the differential pressure sensor (e.g. 263).Furthermore, while not explicitly illustrated, it may be understood thata canister purge valve (e.g. 261) may be maintained closed during thespinning the engine, in order to ensure that air is not drawn from theevaporative emissions system and/or fuel system. Still further, whilenot explicitly shown, for vehicles equipped with exhaust gasrecirculation (EGR) (e.g. high pressure EGR and/or low pressure EGR),one or more valve(s) controlling exhaust gas recirculation may becommanded or maintained closed. Even further, for rotating the engineunfueled, valve timing may be controlled to default values.

With the engine being spun unfueled at the predetermined engine speedfor the predetermined duration, method 700 may proceed to 715. At 715,method 700 may include obtaining measurements of air flow in the intakeand measurements of air flow in the exhaust system. More specifically,the MAF sensor (e.g. 210) may be used at step 720 to obtain a firstbaseline intake air flow measurement(s), while the differential pressuresensor (e.g. 263) may be used at step 725 to obtain a first baselineexhaust air flow measurement(s). Such measurements may be obtained bytaking one or more individual measurements over the predeterminedduration that the engine is being spun unfueled. In an example wheremore than one measurement is obtained while the engine is being spununfueled, such measurements may be averaged or otherwise processed toobtain a high confidence value for the desired measurements.

Such obtained measurements may be stored at the vehicle controller, foruse in conducting the engine system diagnostic, discussed in furtherdetail below and at FIG. 6.

Responsive to obtaining the first baseline intake air flow measurementsand the first baseline exhaust air flow measurements at steps 720 and725, respectively, method 700 may proceed to 730. At 730, method 700 mayinclude stopping spinning the engine unfueled in the forward direction,and may further comprise maintaining the throttle in its currentconfiguration. For example, the motor (e.g. 120) may be commanded tobring the engine to a stop, while the vehicle controller may send asignal to the electronic throttle, commanding or maintaining thethrottle to its current position.

In response to an indication that the engine has spun to rest, method700 may proceed to 735. At 735, method 700 may include rotating orspinning the engine unfueled for a predetermined duration at apredetermined speed (e.g. predetermined RPM), in the reverse direction.Rotating the engine unfueled may comprise rotating the engine in theopposite direction as when the engine is operated to combust air andfuel, and in the opposite direction as the forward engine spin depictedat step 710 of method 700. Rotating the engine unfueled in the reversedirection may include routing air flow through the exhaust system, theengine, the intake manifold, and the intake, in that order. In someexamples, the predetermined duration and the predetermined speed ofengine rotation may be the same duration and speed as that indicatedabove at step 710 of method 700. However, in other examples, thepredetermined duration and the predetermined speed may be different whenspinning or rotating the engine in the reverse direction, as compared tothe forward direction. Similar to that discussed above for rotating theengine in the forward direction, rotating the engine unfueled in thereverse direction may comprise rotating the engine via the motor (e.g.120), where the motor may be powered via the onboard energy storagedevice (e.g. 150), such as a battery. To rotate the engine in reverse,an H-bridge circuit, such as that depicted at FIGS. 5A-5B, may beutilized. The speed of the engine may be controlled via the motor, tothe predetermined speed. Similar to that described above, thepredetermined engine speed may comprise a speed at which robustmeasurements of air flow may be obtained via the MAF sensor (e.g. 210)while the engine is being spun in reverse. Furthermore, while notexplicitly illustrated, it may be understood that the canister purgevalve (e.g. 261) may be maintained closed during the spinning theengine, in order to ensure that air is not routed to the evaporativeemissions system and/or fuel system. Still further, while not explicitlyshown, for vehicles equipped with exhaust gas recirculation (EGR) (e.g.high pressure EGR and/or low pressure EGR), one or more valve(s)controlling exhaust gas recirculation may be commanded or maintainedclosed. Even further, for rotating the engine unfueled in the reversedirection, valve timing may be controlled to default values.

With the engine being spun unfueled in the reverse direction at thepredetermined engine speed, method 700 may proceed to 740. At 740,method 700 may include obtaining measurements of air flow in the intake.More specifically, the MAF sensor (e.g. 210) may be used at step 740 toobtain a second baseline intake air flow measurement(s). Suchmeasurements may be obtained by taking one or more individualmeasurements over the predetermined duration that the engine is beingspun unfueled in the reverse direction. In an example where more thanone measurement is obtained while the engine is being spun unfueled,such measurements may be averaged or otherwise processed to obtain ahigh confidence value for the desired measurements.

Such obtained measurements may be stored at the vehicle controller, foruse in conducting the engine system diagnostic, discussed in furtherdetail at FIG. 6.

Responsive to obtaining the second baseline intake air flow measurementswhile the engine is being spun in reverse, method 700 may proceed to745. At 745, method 700 may include stopping spinning the engineunfueled in the reverse direction, and may further comprise returningthe throttle to a default position or configuration. For example, themotor (e.g. 120) may be commanded via the controller to bring the engineto a stop, while the vehicle controller may send a signal to theelectronic throttle, actuating the throttle to a default position.

As mentioned above, it may be understood that the methodology discussedat FIG. 7 pertains to both obtaining the baseline comparator data, aswell as to conducting the engine system diagnostic subsequent toobtaining the baseline comparator data. As such, the methodology willnot be reiterated for brevity. Thus, it may be understood that theentirety of method 700 may be used in conjunction with FIG. 6 to obtainbaseline comparator data at step 610, as well as to conduct the enginesystem diagnostic at step 625.

More specifically, as discussed, method 700 may be used to first obtainbaseline comparator data, and may then subsequently be used to conductthe engine system diagnostic. Thus, if method 700 is used to obtainbaseline comparator data, it may be understood that at step 720, method700 may include obtaining the first baseline intake air flow, and step725 may include obtaining the first baseline exhaust air flow.Furthermore, at step 740, method 700 may include obtaining secondbaseline intake air flow. Alternatively, if method 700 is used toconduct the engine system diagnostic, then at step 720 method 700 mayinclude obtaining a first intake air flow, and step 725 may includeobtaining a first exhaust air flow. Furthermore, at step 740, method 700may include obtaining a second intake air flow. Discussed herein,obtaining the first intake air flow and the first exhaust air flow maycomprise a first condition, and obtaining the second intake air flow maycomprise a second condition. Additionally, obtaining the first baselineintake air flow and obtaining the first baseline exhaust air flow maycomprise a third condition, and obtaining the second baseline intake airflow may comprise a fourth condition. Thus, the first condition and thethird condition includes spinning the engine in the forward direction,while the second condition and fourth condition includes spinning theengine in the reverse direction.

Accordingly, returning to step 625 of method 600, responsive to anindication that baseline comparator data has been obtained, and thatconditions are met for conducting an engine system diagnostic, method600 may include obtaining the intake flow measurements under bothforward and reverse engine spinning, and obtaining the exhaust flowmeasurements under forward engine spinning, and in some examples duringreverse engine spinning, as discussed with regard to FIG. 7. Responsiveto such measurements being obtained at 625, method 600 may proceed to630. At step 630, method 600 may include interpreting the results of theengine system diagnostic conducted at step 625, according to FIG. 8.

Thus, proceeding to FIG. 8, it illustrates an example lookup table thatmay be utilized to interpret the results of the engine systemdiagnostic. Such a lookup table may be stored at the vehicle controller,for example. As illustrated at FIG. 8, there may be four distinctoutcomes (A-D) that may result from the engine system diagnostic.

Outcome A may include a situation where the measurement of intake airflow as measured by the MAF sensor is substantially equivalent to thebaseline measurement of intake air flow as measured by the MAF sensor,but where exhaust flow as monitored by the differential pressure sensoris greater than the baseline measurement of exhaust flow as measured bythe differential pressure sensor, under conditions where the engine isspun unfueled in the forward direction. In such an example, it may beindicated that there is a source of degradation stemming from the intakemanifold, such as that depicted above at FIG. 3A. As discussed, a sourceof degradation stemming from the intake manifold may result in unmeteredair being introduced into the engine, and as such, air flow in theexhaust system may be greater than that expected under conditions whereno sources of degradation are present (e.g. under baseline conditions).

Outcome A may additionally or alternatively include a situation wheremeasurements of intake air flow as measured by the MAF sensor whilespinning the engine unfueled in the forward direction are substantiallyequivalent to the baseline measurements of intake air flow obtainedduring spinning the engine in the forward direction (see steps 710-725of method 700), but where measurements of intake air flow as measured bythe MAF sensor while spinning the engine unfueled in reverse are lessthan the baseline measurements of intake air flow obtained duringspinning the engine in the reverse direction. In other words, such amethod of inferring whether there is degradation stemming from theintake manifold may be conducted in some examples in a vehicle that doesnot include a differential pressure sensor (e.g. 263). For example,because indicating whether there is a source of degradation involves MAFsensor data under conditions where the engine is spun in a forwarddirection, and then a reverse direction, but may not involvedifferential pressure sensor data, then such a determination of intakemanifold degradation may in some examples be conducted in the absence ofsuch differential pressure sensor data, which may in some examplesinclude an absence of a differential pressure sensor in the exhaustsystem.

Outcome B may include a situation where the measurement of intake airflow as measured by the MAF sensor during spinning the engine unfueledin the forward direction is substantially equivalent to the baselinemeasurement of intake air flow as measured by the MAF sensor duringspinning the engine unfueled in the forward direction, but where exhaustflow as monitored by the differential pressure sensor is less than thebaseline measurement of exhaust flow as measured by the differentialpressure sensor, under conditions of spinning the engine unfueled in theforward direction. In such an example, it may be indicated that there isa source of degradation stemming from the exhaust system, such as thatdepicted above at FIG. 3B. As discussed, a source of degradationstemming from the exhaust system may thus result in exhaust flow beingforced to atmosphere via the source of degradation, prior to reachingthe differential pressure sensor, when the engine is spun unfueled inthe forward direction. Accordingly, such a process may result in adifferential pressure sensor reading below that expected underconditions where no sources of degradation are present (e.g. underbaseline conditions).

Outcome B may additionally or alternatively include a situation wherethe measurement of intake air flow as measured by the MAF sensor duringspinning the engine unfueled in the forward direction is substantiallyequivalent to the baseline measurement of air flow in the intake, butwhere the measurement of intake air flow as measured by the MAF sensorduring spinning the engine unfueled in the reverse direction is greaterthan the baseline measurement of air flow in the intake under similarconditions. In such an example, it may be understood that degradation inthe exhaust system may result in additional air being drawn into theengine via the source of degradation in the exhaust system, and pushedthrough the engine to the intake, under conditions of spinning theengine unfueled in reverse.

Outcome C may include a situation where both air flow in the intake asmeasured by the MAF sensor during spinning the engine unfueled in theforward direction, as well as air flow in the exhaust as measured by thedifferential pressure sensor during spinning the engine unfueled in theforward direction, are less than baseline measurements obtained via theMAF sensor and the differential pressure sensor under conditions ofspinning the engine unfueled in the forward direction. In such anexample, it may be understood that there may be a source of degradationstemming from the engine compartment related to engine operation. Asdiscussed, such a source of degradation may comprise intake and/orexhaust valves that are not sealing properly, compression issues relatedto engine cylinder(s), degraded piston rings, degraded head gasket,undesired camshaft timing, etc. In such a case where the engine isidentified as the source of degradation, the engine may not pump asexpected, thus resulting in overall less air drawn into the engine viathe intake manifold, and a corresponding lower amount of exhaust flowrouted through the exhaust system.

Outcome C may additionally or alternatively include a situation whereintake air flow as measured by the MAF sensor under conditions where theengine is spun unfueled in the forward direction is less than thebaseline MAF sensor data obtained under conditions where the engine isspun unfueled in the forward direction, and where intake air flow isless than the baseline intake air flow under conditions where the engineis being spun unfueled in the reverse direction. In such an example,there may be degradation stemming from the engine compartment, as lessoverall air is indicated to be being drawn into the intake system whenthe engine is spun in the forward direction as compared to baselinemeasurements obtained under similar conditions of forwardengine-spinning, and as less overall air is indicated to be being pushedthrough the intake system when the engine is spun in the reversedirection as compared to baseline measurements obtained under similarconditions of reverse engine-spinning. Thus, it may be understood thatsuch a method of inferring whether there is degradation stemming fromthe engine compartment may be conducted in some examples in a vehiclethat does not include a differential pressure sensor (e.g. 263). Forexample, because indicating whether there is a source of degradationinvolves MAF sensor data under conditions where the engine is spun in aforward direction, and then a reverse direction, but does not involvedifferential pressure sensor data, then such a determination of enginecompartment degradation may in some examples be conducted in the absenceof such differential pressure sensor data, which may in some examplesinclude an absence of a differential pressure sensor in the exhaustsystem.

Outcome D may include a situation where both the air flow in the intakeas measured by the MAF sensor under conditions where the engine is spununfueled in the forward direction, as well as air flow in the exhaustsystem as measured by the differential pressure sensor under conditionswhere the engine is spun unfueled in the forward direction, aresubstantially equivalent to baseline measurements made by the MAF sensorand the differential pressure sensor under conditions where the engineis spun unfueled in the forward direction. In such an example, anabsence of a source of degradation stemming from the intake manifold,exhaust system, and/or engine may be indicated.

Outcome D may additionally or alternatively include a situation whereair flow in the intake as measured by the MAF sensor is substantiallyequivalent to baseline air flow in the intake under conditions ofspinning the engine unfueled in the forward direction, and where airflow in the intake as measured by the MAF sensor is substantiallyequivalent to baseline air flow in the intake under conditions ofspinning the engine unfueled in the reverse direction. Thus, it may beunderstood that such a method of inferring whether there is an absenceof degradation stemming from the intake manifold, engine, or exhaustsystem may be conducted in some examples in a vehicle that does notinclude a differential pressure sensor (e.g. 263). For example, becauseindicating whether there is an absence of degradation involves MAFsensor data under conditions where the engine is spun in a forwarddirection, and then a reverse direction, but does not involvedifferential pressure sensor data, then such a determination of theabsence of engine system degradation may in some examples be conductedin the absence of such differential pressure sensor data, which may insome examples include an absence of a differential pressure sensor inthe exhaust system.

It may be understood that in each of the above-discussed potentialoutcomes A-D, sensor readings that are substantially equivalent to theirrespective baseline measurements may comprise measurements being withina certain range of each other, for example less than or equal to a 5%difference in measurements over the span of the engine systemdiagnostic, or less than or equal to a 5% difference in averagedmeasurements comprising the span of the engine system diagnostic. Thus,it may be further understood that data less than/greater than baselinedata may comprise data greater than a 5% difference from the baselinedata.

It may be further understood that there may be circumstances where itmay be desirable to conduct the engine system diagnostic or to obtainbaseline comparator data by spinning the engine unfueled in the forwarddirection, but not in the reverse direction, or vice versa. For example,consider a situation where battery power is low or limited, and thus itmay not be desirable to spin the engine in both the forward and reversedirections, to conduct the engine system diagnostic. Instead, it may bedesirable to only spin the engine unfueled in the forward direction, forexample. In such an example, degradation of either the intake, enginecompartment, or exhaust system may be effectively diagnosed provided thevehicle includes the MAF sensor and the differential pressure sensor.However, in situations where the vehicle does not include both the MAFsensor and the differential pressure sensor, then the MAF sensor may beutilized to infer the presence or absence of degradation stemming fromthe intake, engine compartment, or exhaust system, under conditions offorward and reverse engine spinning (for obtaining baseline intake andexhaust flow, and for conducting the engine system diagnostic undersimilar conditions), as discussed above.

Returning to FIG. 6, subsequent to interpreting the results of theengine system diagnostic at step 630 of method 600, method 600 mayproceed to 635. At 635, method 600 may include adjusting vehicleoperating parameters according to the results of the engine systemdiagnostic. As examples, provided that a source of degradation isidentified in the intake manifold, exhaust system, and/or engine, a MILmay be illuminated on the vehicle dash alerting the vehicle operator ofa request to service the vehicle.

If a source of degradation is indicated as stemming from the intakemanifold, the vehicle controller may adjust throttle position in someexamples during fueled engine operation, in order to account for theunmetered air entering the engine via the source of degradation.

In other examples, where the source of degradation is indicated asstemming from either the intake manifold, exhaust system, or enginecompartment, adjusting vehicle operating parameters may include thevehicle controller commanding an electric mode of operation asfrequently as possible, to mitigate a potential release of undesiredemissions to atmosphere, and/or to mitigate potential mechanical issueswith the engine under circumstances where the engine is ingesting agreater amount of air than desired, or to mitigate issues alreadypresent in the engine compartment.

Thus, in one example, a method may include spinning an engine of avehicle unfueled in a forward and a reverse direction to obtain a firstintake air flow and a second intake air flow, respectively, in an intakeof the engine. The method may further include indicating a source ofdegradation stemming from one of the engine, an intake manifold of theengine, or an exhaust system of the engine based on both the first airflow and the second air flow.

In such a method, prior to spinning the engine unfueled in the forwardand the reverse direction to obtain the first intake air flow and thesecond intake air flow, the method may include obtaining a set ofbaseline comparator data that includes spinning the engine unfueled inthe forward and the reverse direction to obtain a first baseline intakeair flow and a second baseline intake air flow. It may be understoodthat spinning the engine unfueled in the forward and reverse directionmay be conducted via a motor powered by a battery.

In such a method, obtaining the first baseline intake air flow and thesecond baseline intake air flow may include spinning the engine in theforward and the reverse direction, respectively, under a substantiallyequivalent set of conditions as that for obtaining the first intake airflow and the second intake air flow. For example, the substantiallyequivalent set of conditions may include spinning the engine in theforward direction at a first predetermined speed and for a firstpredetermined duration of time, spinning the engine in the reversedirection at a second predetermined speed and for a second predeterminedduration of time, and controlling a throttle positioned in the intakemanifold to a predetermined position during spinning the engine in theforward and reverse directions.

In such a method, obtaining the first intake air flow, the second intakeair flow, the first baseline intake air flow, and the second baselineintake air flow may include sealing the intake manifold and the enginefrom an evaporative emissions system of the vehicle, and sealing theengine, intake manifold, and exhaust system from an exhaust gasrecirculation system, configured to recirculate at least a portion ofexhaust gas from the engine to the intake manifold under predeterminedconditions of engine operation.

In such a method, it may be understood that obtaining the set ofbaseline comparator data includes conditions where the intake manifoldof the engine, the engine, and the exhaust system of the engine areindicated to be free from the source of degradation.

In such a method, the engine, the intake manifold, and the exhaustsystem are indicated to be free from the source of degradationresponsive to the first intake air flow being substantially equivalentto the first baseline intake air flow and the second intake air flowbeing substantially equivalent to the second baseline intake air flow.Alternatively, the source of degradation may be indicated to be theintake manifold responsive to the first intake air flow beingsubstantially equivalent to the first baseline intake air flow, butwhere the second intake air flow is less than the second baseline intakeair flow. In another example, the source of degradation may be indicatedto be the engine responsive to both the first intake air flow being lessthan the first baseline intake air flow and the second intake air flowbeing less than the second baseline intake air flow. In still anotherexample, the source of degradation may be indicated to be the exhaustsystem responsive to the first intake air flow being substantiallyequivalent to the first baseline intake air flow, but where the secondintake air flow is greater than the second baseline intake air flow.

Another example of a method comprises routing a first air flow throughan intake of an engine, intake manifold of the engine, the engine, andan exhaust system of the engine, in that order in a first condition;routing a second air flow through the exhaust system, the engine, theintake manifold, and the intake, in that order, in a second condition;indicating a first intake air flow in the first condition and a secondintake air flow in the second condition; indicating a first exhaust airflow in the first condition; and diagnosing a presence or an absence ofdegradation stemming from one of the intake manifold, the engine, or theexhaust system as a function of two or more of the first intake airflow, the second intake air flow, and/or the first exhaust air flow.

In such a method, the method may further comprise in a third condition,indicating a first baseline intake air flow and indicating a firstbaseline exhaust air flow; in a fourth condition, indicating a secondbaseline intake air flow. In such an example, the third condition mayinclude routing a third air flow through the intake of the engine,intake manifold of the engine, the engine, and the exhaust system of theengine, in that order, and the fourth condition may include routing afourth air flow through the exhaust system, the engine, the intakemanifold, and the intake, in that order.

In such a method, the first condition and the third condition mayinclude rotating the engine unfueled via a motor in a forward directionto route the first air flow through the intake, the intake manifold, theengine, and the exhaust system, in that order. In such a method, thesecond condition and the fourth condition may include rotating theengine unfueled via the motor in a reverse direction to route the secondair flow through the exhaust system, the engine, the intake manifold,and the intake, in that order.

In such a method, it may be understood that routing the first air flowincludes routing the first air flow for a first predetermined duration,and where routing the third air flow includes routing the third air flowfor the first predetermined duration. As an example, routing the secondair flow may include routing the second air flow for a secondpredetermined duration, routing the fourth air flow may include routingthe fourth air flow for the second predetermined duration, where thefirst predetermined duration is either the same or different than thesecond predetermined duration. In such a method, each of the firstcondition, second condition, third condition, and fourth condition mayinclude controlling a throttle position in the intake of the vehicle toa predetermined open position. In such a method, each of the firstcondition, second condition, third condition, and fourth condition mayinclude sealing an evaporative emissions system from the intake, intakemanifold, engine, and exhaust system, the evaporative emissions systemconfigured to capture and store fuel vapors from a fuel system of thevehicle, and wherein each of the first condition, second condition,third condition, and fourth condition includes sealing the intake,intake manifold, engine, and exhaust system from an exhaust gasrecirculation system, the exhaust gas recirculation system configured toroute at least a portion of exhaust gases from the engine to the intakemanifold.

In such a method, the method may further comprise indicating thepresence of degradation stemming from the intake manifold responsive tothe first intake air flow being substantially equivalent to the firstbaseline intake air flow and where the first exhaust air flow is greaterthan the first baseline exhaust air flow, and/or where the first intakeair flow is substantially equivalent to the first baseline intake airflow and where the second intake air flow is less than the secondbaseline intake air flow. Alternatively, the method may includeindicating the presence of degradation stemming from the exhaust systemresponsive to the first intake air flow being substantially equivalentto the first baseline intake air flow and where the first exhaust airflow is less than the first baseline exhaust air flow, and/or where thefirst intake air flow is substantially equivalent to the first baselineintake air flow and where the second intake air flow is greater than thesecond baseline intake air flow. In still another example, the methodmay include indicating the presence of degradation stemming from theengine responsive to the first intake air flow being less than the firstbaseline intake air flow and responsive to the first exhaust air flowbeing less than the first baseline exhaust air flow, and/or where thefirst intake air flow is less than the first baseline intake air flowand where the second intake air flow is less than the second baselineintake air flow.

In such a method, it may be understood that the third condition and thefourth condition may be conducted under conditions where degradation inthe intake manifold, engine and exhaust system is not already indicated.It may be further understood that the first condition, second condition,third condition, and fourth condition may all be conducted underconditions where the vehicle is not occupied and where the vehicle isnot in motion. It may be further understood that the first intake airflow, the first baseline intake air flow, the second intake air flow,and the second baseline intake air flow may be indicated via a mass airflow sensor positioned in the intake manifold of the engine, and wherethe first exhaust air flow and the first baseline exhaust air flow areindicated via a differential pressure sensor positioned in the exhaustsystem.

Turning now to FIG. 9, an example timeline 900 is shown for obtainingbaseline comparator measurements, as well as conducting an engine systemdiagnostic in a vehicle, according to the methods depicted herein andwith reference to FIGS. 6-8, and as applied to the systems depictedherein and with reference to FIGS. 1-5B. Timeline 900 includes plot 905,indicating whether an engine off, or is on and spinning in a forward(fwd) or reverse (rev) direction, over time. Timeline 900 furtherincludes plot 910, indicating whether fuel injection to one or moreengine cylinders, is on, or off, over time. Timeline 900 furtherincludes plot 915, indicating whether a throttle (e.g. 262) is open,closed, or some level between open and closed (e.g. some fraction offully open). Timeline 900 further includes plot 920, indicating anengine speed (RPM), over time. Engine speed may be either 0 (fullystopped), or may be greater (+) than fully stopped. Timeline 900 furtherincludes plot 925, indicating air flow in the intake of the vehicle, asmonitored by the MAF sensor (e.g. 210). The MAF sensor may indicate anabsence of air flow (0), or may indicate air flow greater (+) than theabsence of air flow. It may be understood that air flow may either beair flow to the engine (engine spinning in the forward direction) fromthe intake, or air flow from the engine and exhaust system to the intake(engine spinning in the reverse direction).

Timeline 900 further includes plot 930, indicating air flow in theexhaust system of the vehicle, as monitored by the differential pressuresensor (e.g. 263). The differential pressure sensor may indicate anabsence of air flow (0), or may indicate air flow greater (+) than theabsence of air flow. It may be understood that air flow in the exhaustsystem may either comprise air flow from the engine to the exhaustsystem (engine spinning in the forward direction) or air flow to theengine from the exhaust system (engine spinning in the reversedirection). Timeline 900 further includes plot 935, indicating anair-fuel ratio as monitored via an exhaust gas sensor (e.g. 237), overtime. Air-fuel ratio may be either stoichiometric (ideal ratio of air tofuel that burns all fuel with no excess air), or may be either rich orlean of stoichiometry.

Timeline 900 further includes plot 940, indicating whether conditionsare indicated to be met for obtaining baseline comparator data, plot945, indicating whether conditions are indicated to be met forconducting the engine system diagnostic, plot 950, indicating whetherthe vehicle is occupied, and plot 955, indicating whether a source ofdegradation is present in the engine system, over time. The source maybe the engine, intake manifold (intake) or exhaust system (exhaust).

At time t0, the engine is off (plot 905), and accordingly, fuel is notbeing injected into engine cylinders (plot 910), and engine speed is 0RPM (plot 920). While not explicitly shown, it may be understood that attime t0, the vehicle is also not being propelled via a motor. A positionof the throttle is substantially closed, reflecting a position of thethrottle in an engine off/vehicle off state. With the engine off, thereis no air-fuel ratio to measure, and thus an air-fuel ratio is notindicated at time t0. Similarly, a MAF sensor positioned in an intakemanifold downstream of the throttle is not registering any air flow(plot 925) in the intake, and the differential pressure sensor is alsonot registering any air flow in the exhaust system (plot 930). At timet0, conditions are not indicated to be met for obtaining baselinecomparator data (plot 940), and conditions are further not indicated tobe met for conducting an engine system diagnostic test (plot 945). Thevehicle is not indicated to be occupied (plot 950), and degradation isnot indicated in the engine system (plot 955).

At time t1, conditions are indicated to be met for obtaining baselinecomparator data (plot 940). Conditions being met for obtaining baselinecomparator data have been discussed with regard to step 605 of method600, and for brevity, will not be reiterated here. However, it may beunderstood that in this example timeline 900, conditions being met mayinclude a situation where a predetermined duration of time has elapsedsince a key-off event, where the controller is woken up in order toobtain the baseline comparator data. With conditions being met forobtaining baseline comparator data, the engine may be activated to bespun in a forward (or default) direction. More specifically, the vehiclecontroller may command the motor (e.g. 120) to rotate the engineunfueled in the forward or default direction. As such, fuel injection tothe cylinders of the engine may be maintained off (plot 910). The motormay control engine speed to a predetermined engine speed (plot 920).Furthermore, the throttle may be controlled to a predetermined throttleposition (plot 915), as discussed above with regard to step 705 ofmethod 700 depicted at FIG. 7.

The time period between time t1 and t2 may comprise a predetermined timeperiod for spinning the engine in the forward direction unfueled. Byspinning the engine unfueled in the forward direction, air may be drawnthrough the intake and into the engine, before being routed to theexhaust system. As fuel injection (and spark) is not being provided tothe engine cylinders, the air-fuel ratio indicates a lean condition(plot 935), as indicated by the exhaust gas sensor (e.g. 237). Air flowin the intake is monitored by the MAF sensor between time t1 and t2(plot 925), and air flow in the exhaust system is monitored via thedifferential pressure sensor (plot 930). As discussed, such measurementsmay be stored at the controller of the vehicle, such that subsequentmeasurements of air flow in the intake and subsequent measurements ofair flow in the exhaust system may be compared to the baselinemeasurements. In this way, potential sources of degradation stemmingfrom the intake manifold, exhaust system, or engine, may be pinpointed.

Subsequent to the predetermined time duration of spinning the engineunfueled in the forward direction elapsing, the engine is controlled viathe electric motor to 0 RPM. In other words, the engine is spun to restbetween time t2 and t3. However, the throttle is maintained in itscurrent state, in order to avoid the throttle being closed, then openedagain in order to spin the engine in the reverse direction.

Between time t2 and t3, with the engine spinning to rest, air flow inthe intake (plot 925) and air flow in the exhaust system (plot 930)returns to 0, or no flow. After the engine is spun to rest, at time t3,the engine is controlled to spin unfueled in the reverse direction. Asdiscussed an H-bridge circuit such as that depicted at FIGS. 5A-5B maybe utilized to enable the motor to spin the engine unfueled in thereverse direction.

The time period between time t3 and t4 may comprise a predetermined timeperiod for spinning the engine in the reverse direction unfueled. Byspinning the engine unfueled in the reverse direction, air may be drawnthrough the exhaust system and into the engine, before being routed outof the engine to engine intake. As air is drawn across the exhaust gassensor, a lean condition is indicated (plot 935). Air flow in the intakeis monitored by the MAF sensor between time t3 and t4 (plot 925), andair flow in the exhaust system is monitored via the differentialpressure sensor (plot 930). As discussed, such measurements may bestored at the controller of the vehicle, such that subsequentmeasurements of air flow in the intake and subsequent measurements ofair flow in the exhaust system may be compared to the baselinemeasurements. In this way, potential sources of degradation stemmingfrom the intake manifold, exhaust system, or engine, may be pinpointed,as discussed above and which will be discussed further below.

Subsequent to the predetermined time duration of spinning the engineunfueled in the reverse direction elapsing, the engine is controlled viathe electric motor to 0 RPM. In other words, the engine is spun to restbetween time t4 and t5. Furthermore, the throttle is actuated via thecontroller to a default configuration, which in this example includes aconfiguration that the throttle was at prior to obtaining the baselinecomparator data. With the engine being spun to rest between time t4 andt5, air flow decreases to no flow in the intake as measured by the MAFsensor, and air flow in the exhaust system decreases to no flow asmeasured by the differential pressure sensor. As baseline comparatordata has been obtained for both conditions of spinning the engineunfueled in the forward and reverse directions, and stored at thecontroller, and with the predetermined time duration elapsing at timet4, conditions are no longer indicated to be met for obtaining thebaseline comparator data.

At time t5, the vehicle becomes occupied (plot 950). Such an indicationmay be provided via door sensors, seat load cells, onboard camera(s),etc. Furthermore, the engine is turned on (plot 905), with fuelinjection provided to one or more engine cylinders (plot 910). In otherwords, at time t5, a vehicle operator has entered the vehicle andstarted the engine, with the intent to drive the vehicle. With fuelinjection provided to the engine cylinders, it may be understood thatthe engine is operating in the forward direction, indicated at plot 905.

Between time t5 and t6, the vehicle is driven, and accordingly throttleposition (plot 915) varies as a function of driver demand, and enginespeed (plot 920) is controlled as a function of driver demand. With theengine in operation, both the MAF sensor (plot 925) and the differentialpressure sensor (plot 930) measure intake air flow, and exhaust flow,respectively, which vary as a function of driver demand.

Between time t5 and t6, air-fuel ratio is maintained substantiallyequivalent to stoichiometric air-fuel ratio. However, at time t6, theair-fuel ratio switches lean. As discussed above, a change in air-fuelratio may be indicative of potential degradation in the engine system.Thus, it may be understood that, in response to the change in air-fuelratio indicated at time t6, such a result may be stored at the vehiclecontroller, such that an engine system diagnostic may be initiated atthe next opportunity where conditions are indicated to be met forconducting the engine system diagnostic.

Between time t6 and t7, the vehicle is continued to be operated with theengine combusting air and fuel. In some examples, responsive to adisturbance in air-fuel ratio, adaptive fuel learning may correct thelean air-fuel ratio, indicated by dashed line 936. However, in otherexamples, the vehicle may not include adaptive fuel learning.

At time t7, the engine is turned off (plot 905), and fueling to theengine is stopped (plot 910). Furthermore, at time t7, the vehicle onceagain becomes unoccupied (plot 950).

After some time, at time t8, conditions are indicated to be met forconducting the engine system diagnostic as discussed above with regardto step 615 of method 600. For brevity, such conditions will not bereiterated here. However, it may be understood in this example timeline900, conditions being met may include a situation where a predeterminedduration of time has elapsed since a key-off event, where the controlleris woken up in order to conduct the engine system diagnostic.Accordingly, with conditions being met for conducting the engine systemdiagnostic, the engine is activated to be spun in a forward or defaultdirection at time t8. More specifically, the vehicle controller maycommand the motor (e.g. 120) to rotate the engine unfueled in theforward or default direction. As such, fuel injection to the cylindersof the engine may be maintained off (plot 910). The motor may controlengine speed (plot 920) to the same engine speed as engine speed duringobtaining the baseline comparator data (e.g. engine speed between timet1 and t2). Furthermore, the throttle may be controlled to the samepredetermined throttle position, as the throttle position duringobtaining the baseline comparator data (e.g. throttle position betweentime t1 and t2).

The time period between time t8 and t9 may comprise the predeterminedtime period for spinning the engine unfueled in the forward directionunfueled to conduct the engine system diagnostic. More specifically, thepredetermined time period for spinning the engine in the forwarddirection unfueled to conduct the engine system diagnostic may comprisethe same predetermined time period for spinning the engine unfueled inthe forward direction to obtain the baseline comparator data (e.g.between time t1 and t2). As discussed, by spinning the engine unfueledin the forward direction, air may be drawn through the intake and intothe engine, before being routed to the exhaust system. As fuel injection(and spark) is not being provided to the engine cylinders, the air-fuelratio indicates a lean condition (plot 935), as indicated by the exhaustgas sensor (e.g. 237). Air flow in the intake is monitored by the MAFsensor between time t8 and t9 (plot 925), and air flow in the exhaustsystem is monitored via the differential pressure sensor (plot 930). Asdiscussed, such measurements may be stored at the controller of thevehicle, such that the measurements of air flow in the intake andexhaust system obtained during conducting the engine diagnostic byspinning the engine unfueled in the forward direction may be compared tothe baseline measurements obtained under the same conditions. In thisway, potential sources of degradation stemming from the intake manifold,exhaust system, or engine, may be pinpointed.

Subsequent to the predetermined time duration of spinning the engineunfueled in the forward direction elapsing, the engine is controlled viathe electric motor to 0 RPM. In other words, the engine is spun to restbetween time t9 and t10. However, the throttle is maintained in itscurrent state, in order to avoid the throttle being closed, then openedagain in order to spin the engine in the reverse direction forconducting the engine system diagnostic.

Between time t9 and t10, with the engine spinning to rest, air flow inthe intake (plot 925) and air flow in the exhaust system (plot 930)returns to 0, or no flow. After the engine is spun to rest, at time t10,the engine is controlled to spin unfueled in the reverse direction. Asdiscussed above, an H-bridge circuit such as that depicted at FIGS.5A-5B may be utilized to enable the motor to spin the engine unfueled inthe reverse direction.

The time period between time t10 and t11 may comprise the predeterminedtime period for spinning the engine in the reverse direction unfueledfor conducting the engine system diagnostic. It may be understood thatthe predetermined time period for spinning the engine in the reversedirection for conducting the engine system diagnostic may comprise thesame predetermined duration of spinning the engine unfueled in thereverse direction to obtain the baseline comparator data. By spinningthe engine unfueled in the reverse direction, air may be drawn throughthe exhaust system and into the engine, before being routed out of theengine to engine intake. As air is drawn across the exhaust gas sensor,a lean condition is indicated (plot 935). Air flow in the intake ismonitored by the MAF sensor between time t11 and t12 (plot 925), and airflow in the exhaust system is monitored via the differential pressuresensor (plot 930). As discussed, such measurements may be stored at thecontroller of the vehicle, for comparison to baseline measurements ofair flow in the intake and air flow in the exhaust system under similarconditions.

With the predetermined time duration of spinning the engine unfueled inthe reverse direction elapsing, conditions are no longer indicated to bemet for conducting the engine system diagnostic (plot 945). Accordingly,at time t11, the data acquired between time t8 and t9 related to airflow in the intake is compared to data acquired between time t1 and t2.Furthermore, the data acquired between time t10 and t11 is compared todata acquired between time t3 and t4. As discussed, a lookup table, suchas lookup table 800 depicted at FIG. 8 may be utilized to diagnose thepresence or absence of degradation in the engine system. Morespecifically, the data acquired between time t1 and t2 comprisesbaseline comparator data regarding air flow in the intake and exhaustsystem while the engine is spun unfueled in the forward direction. Suchbaseline comparator data may comprise an averaged or otherwise processedfirst MAF baseline, or first intake air flow baseline, represented byline 926, and an averaged or otherwise processed first differentialpressure sensor baseline, or first exhaust flow baseline, represented byline 931. Similarly, the data acquired between time t3 and t4 comprisesbaseline comparator data regarding air flow in the intake and exhaustsystem while the engine is spun unfueled in the reverse direction. Suchbaseline comparator data may comprise an averaged or otherwise processedsecond MAF baseline, or second intake flow baseline, represented by line927. While not explicitly illustrated, an averaged or otherwiseprocessed second differential pressure sensor baseline, or secondexhaust flow baseline, may in some examples be generated via thecontroller.

As illustrated, the air flow in the intake (plot 925) acquired duringthe engine system diagnostic where the engine was spun unfueled in theforward direction (between time t8 and t9) is substantially equivalentto the first intake air flow baseline, represented by line 926. However,the air flow in the intake acquired during the engine system diagnosticwhere the engine was spun unfueled in the reverse direction (betweentime t10 and t11) is lower than the second intake air flow baseline,represented by line 927. Turning to FIG. 8, outcome A depicts asituation where intake air flow is substantially equivalent to baselineintake air flow when the engine is spun in the forward direction, butwhere intake air flow is less than the baseline when the engine is spunin the reverse direction. Accordingly, at time t11, degradation of theintake manifold is indicated (plot 955). The data from air flow in theexhaust system obtained during spinning the engine in the forwarddirection supports such an indication. Specifically, air flow in theintake (plot 925) acquired during the engine system diagnostic where theengine was spun unfueled in the forward direction (between time t8 andt9) is substantially equivalent to the first intake air flow baseline,represented by line 926. However, the air flow in the exhaust system(plot 930) acquired during the engine system diagnostic where the enginewas spun unfueled in the forward direction (between time t8 and t9) isgreater than the first exhaust flow baseline, represented by line 931.Turning to FIG. 8, outcome A depicts a situation where intake air flowis substantially equivalent to baseline intake air flow when the engineis spun unfueled in the forward direction, but where air flow in theexhaust is greater than baseline exhaust flow under the same conditions.

Thus, at time t11, degradation is indicated in the intake manifold (plot955), and with conditions for conducting the engine system diagnostic nolonger indicated to be met (plot 945), the engine is deactivated (plot905), and the motor spins the engine to rest between time t11 and t12.Furthermore, throttle position (plot 915) may be controlled or actuatedvia the controller to its default configuration. As the engine isspinning to rest between time t11 and t12, engine speed goes to 0 RPM(plot 920), air flow in the intake goes to no flow (plot 925), and airflow in the exhaust system goes to no flow (plot 930). Subsequent totime t12 the engine is maintained off and the vehicle remainsunoccupied. While not explicitly shown, the vehicle controller may beput to sleep responsive to conducting the engine system diagnostic.

While not explicitly discussed, it may be understood that in someexamples, data acquired related to exhaust flow during spinning theengine unfueled in reverse, may be acquired to obtain baseline exhaustflow while spinning the engine unfueled in reverse, and may additionallybe acquired to obtain exhaust flow while spinning the engine unfueled inreverse to conduct the engine system diagnostic. For example, consider asituation where air flow in the exhaust system during spinning theengine unfueled in the forward direction is greater than baseline airflow in the exhaust system acquired under the same circumstances, andwhere air flow in the exhaust system during spinning the engine unfueledin the reverse direction is substantially equivalent to baseline airflow in the exhaust system acquired under the same circumstances. Suchan indication may be indicative of degradation in the intake manifold.In another example, consider a situation where air flow in the exhaustsystem obtained during both spinning the engine unfueled in the forwarddirection, and the reverse direction, is lower than baseline dataobtained under the same conditions. In such an example, such anindication may be indicative of degradation in the engine systemcompartment. In still another example, consider a situation where airflow in the exhaust system obtained during spinning the engine unfueledin the forward direction is less than baseline air flow in the exhaustsystem obtained under similar circumstances, and where air flow in theexhaust system obtained during spinning the engine unfueled in thereverse direction is substantially equivalent to baseline air flow inthe exhaust system obtained under similar circumstances. In such anexample, such an indication may be indicative of degradation in theexhaust system.

In this way, degradation stemming from one of the intake manifold,exhaust system (upstream of the differential pressure sensor anddownstream of the engine), or engine of the engine system may bepinpointed by making use of intake air flow measurements and exhaustflow measurements, in comparison to baseline intake air flow andbaseline exhaust flow measurements, where the baseline intake air flowand exhaust flow measurements are obtained under conditions where theengine system is free from degradation. By pinpointing the source ofdegradation, customer satisfaction may be improved, as time spentworking on the vehicle via a technician may be reduced. Furthermore,pinpointing the source of degradation may result in a reduction ofrelease of undesired emissions to atmosphere.

The technical effect is to recognize that a mass air flow sensorpositioned in the intake of an engine may be utilized to effectivelydiagnose degradation in the intake of a vehicle, by monitoring air flowin the intake under conditions where the engine is spun unfueled in theforward direction, and then the reverse direction (or vice versa), andcomparing the air flow to baseline air flow under similar conditions offorward and reverse engine spinning. A further technical effect is torecognize that degradation of the exhaust system and/or enginecompartment may be indicated in similar fashion by monitoring air flowin the intake under conditions of spinning the engine unfueled in theforward and reverse directions.

Another technical effect is to recognize that an engine systemdiagnostic may in some examples be conducted by only spinning the enginein the forward direction, and monitoring air flow in the intake and airflow in the exhaust system, and comparing said air flow to baseline airflow in the intake and exhaust system, under similar conditions. Forexample, it is recognized that a mass air flow sensor positioned in theintake manifold of an engine may not be able to effectively diagnose asource of degradation stemming from the intake manifold by spinning theengine in a forward direction, unless such a measurement of mass airflow is considered in conjunction with a pressure sensor or other sensorto monitor air flow in the exhaust system. Similarly, a source ofdegradation stemming from an engine, or exhaust system may not bedirectly inferable under conditions where the engine is spun in theforward direction (but not the reverse direction) unless measurements ofintake air flow and exhaust flow are considered together. Thus, atechnical effect is to recognize that in some examples, an engine systemdiagnostic may be conducted by spinning the engine unfueled in theforward direction, but not in the reverse direction, which may bedesirable in situations where battery power is low or limited. In allexamples (e.g. source of degradation stemming from the intake manifold,exhaust system, or engine), a further technical effect is to recognizethat measurements of intake air flow and exhaust flow may be compared tobaseline measurements of intake air flow and exhaust flow obtained undersimilar conditions, such that by comparing both intake air flow andexhaust flow to baseline intake air flow and exhaust flow measurements,respectively, a determination of a source of degradation may beindicated. In this way, a source of degradation stemming from the intakemanifold, exhaust system, or engine may be conclusively diagnosed.

The systems described herein, and with reference to FIGS. 1-5B, alongwith the methods described herein, and with reference to FIGS. 6-7 mayenable one or more systems and one or more methods. In one example, amethod comprises spinning an engine of a vehicle unfueled in a forwardand a reverse direction to obtain a first intake air flow and a secondintake air flow, respectively, in an intake of the engine; andindicating a source of degradation stemming from one of the engine, anintake manifold of the engine, or an exhaust system of the engine basedon both the first air flow and the second air flow. In a first exampleof the method, the method further comprises prior to spinning the engineunfueled in the forward and the reverse direction to obtain the firstintake air flow and the second intake air flow, obtaining a set ofbaseline comparator data that includes spinning the engine unfueled inthe forward and the reverse direction to obtain a first baseline intakeair flow and a second baseline intake air flow; and wherein spinning theengine unfueled in the forward and the reverse direction is conductedvia a motor powered by a battery. A second example of the methodoptionally includes the first example, and further includes whereinobtaining the first baseline intake air flow and the second baselineintake air flow includes spinning the engine in the forward and thereverse direction, respectively, under a substantially equivalent set ofconditions as that for obtaining the first intake air flow and thesecond intake air flow, where the substantially equivalent set ofconditions includes spinning the engine in the forward direction at afirst predetermined speed and for a first predetermined duration oftime, spinning the engine in the reverse direction at a secondpredetermined speed and for a second predetermined duration of time, andcontrolling a throttle positioned in the intake manifold to apredetermined position during spinning the engine in the forward andreverse directions. A third example of the method optionally includesany one or more or each of the first and second examples, and furtherincludes wherein spinning the engine unfueled in the forward and thereverse direction to obtain the first intake air flow, the second intakeair flow, the first baseline intake air flow, and the second baselineintake air flow further comprises: sealing the intake manifold and theengine from an evaporative emissions system of the vehicle; and sealingthe engine, intake manifold, and exhaust system from an exhaust gasrecirculation system, configured to recirculate at least a portion ofexhaust gas from the engine to the intake manifold under predeterminedconditions of engine operation. A fourth example of the methodoptionally includes any one or more or each of the first through thirdexamples, and further includes wherein obtaining the set of baselinecomparator data is conducted under conditions where the intake manifoldof the engine, the engine, and the exhaust system of the engine areindicated to be free from the source of degradation. A fifth example ofthe method optionally includes any one or more or each of the firstthrough fourth examples, and further includes wherein the engine, theintake manifold, and the exhaust system are indicated to be free fromthe source of degradation responsive to the first intake air flow beingsubstantially equivalent to the first baseline intake air flow and thesecond intake air flow being substantially equivalent to the secondbaseline intake air flow. A sixth example of the method optionallyincludes any one or more or each of the first through fifth examples,and further includes wherein the source of degradation is indicated tobe the intake manifold responsive to the first intake air flow beingsubstantially equivalent to the first baseline intake air flow, butwhere the second intake air flow is less than the second baseline intakeair flow. A seventh example of the method optionally includes any one ormore or each of the first through sixth examples, and further includeswherein the source of degradation is indicated to be the engineresponsive to both the first intake air flow being less than the firstbaseline intake air flow and the second intake air flow being less thanthe second baseline intake air flow. An eighth example of the methodoptionally includes any one or more or each of the first through seventhexamples, and further includes wherein the source of degradation isindicted to be the exhaust system responsive to the first intake airflow being substantially equivalent to the first baseline intake airflow, but where the second intake air flow is greater than the secondbaseline intake air flow.

Another example of a method comprises routing a first air flow throughan intake of an engine, intake manifold of the engine, the engine, andan exhaust system of the engine, in that order in a first condition;routing a second air flow through the exhaust system, the engine, theintake manifold, and the intake, in that order, in a second condition;indicating a first intake air flow in the first condition and a secondintake air flow in the second condition; indicating a first exhaust airflow in the first condition; and diagnosing a presence or an absence ofdegradation stemming from one of the intake manifold, the engine, or theexhaust system as a function of two or more of the first intake airflow, the second intake air flow, and/or the first exhaust air flow. Ina first example of the method, the method further comprises in a thirdcondition, indicating a first baseline intake air flow and indicating afirst baseline exhaust air flow; in a fourth condition, indicating asecond baseline intake air flow; and wherein the third conditionincludes routing a third air flow through the intake of the engine,intake manifold of the engine, the engine, and the exhaust system of theengine, in that order; and wherein the fourth condition includes routinga fourth air flow through the exhaust system, the engine, the intakemanifold, and the intake, in that order. A second example of the methodoptionally includes the first example, and further includes wherein thefirst condition and the third condition includes rotating the engineunfueled via a motor in a forward direction to route the first air flowthrough the intake, the intake manifold, the engine, and the exhaustsystem, in that order, and where the second condition and the fourthcondition includes rotating the engine unfueled via the motor in areverse direction to route the second air flow through the exhaustsystem, the engine, the intake manifold, and the intake, in that order.A third example of the method optionally includes any one or more oreach of the first and second examples, and further includes whereinrouting the first air flow includes routing the first air flow for afirst predetermined duration, and where routing the third air flowincludes routing the third air flow for the first predeterminedduration; wherein routing the second air flow includes routing thesecond air flow for a second predetermined duration, where routing thefourth air flow includes routing the fourth air flow for the secondpredetermined duration, where the first predetermined duration is eitherthe same or different than the second predetermined duration; whereineach of the first condition, second condition, third condition, andfourth condition includes controlling a throttle position in the intakeof the vehicle to a predetermined open position; and wherein each of thefirst condition, second condition, third condition, and fourth conditionincludes sealing an evaporative emissions system from the intake, intakemanifold, engine, and exhaust system, the evaporative emissions systemconfigured to capture and store fuel vapors from a fuel system of thevehicle, and wherein each of the first condition, second condition,third condition, and fourth condition includes sealing the intake,intake manifold, engine, and exhaust system from an exhaust gasrecirculation system, the exhaust gas recirculation system configured toroute at least a portion of exhaust gases from the engine to the intakemanifold. A fourth example of the method optionally includes any one ormore or each of the first through third examples, and further comprisesindicating the presence of degradation stemming from the intake manifoldresponsive to the first intake air flow being substantially equivalentto the first baseline intake air flow and where the first exhaust airflow is greater than the first baseline exhaust air flow, and/or wherethe first intake air flow is substantially equivalent to the firstbaseline intake air flow and where the second intake air flow is lessthan the second baseline intake air flow. A fifth example of the methodoptionally includes any one or more or each of the first through fourthexamples, and further comprises indicating the presence of degradationstemming from the exhaust system responsive to the first intake air flowbeing substantially equivalent to the first baseline intake air flow andwhere the first exhaust air flow is less than the first baseline exhaustair flow, and/or where the first intake air flow is substantiallyequivalent to the first baseline intake air flow and where the secondintake air flow is greater than the second baseline intake air flow. Asixth example of the method optionally includes any one or more or eachof the first through fifth examples, and further comprises indicatingthe presence of degradation stemming from the engine responsive to thefirst intake air flow being less than the first baseline intake air flowand responsive to the first exhaust air flow being less than the firstbaseline exhaust air flow, and/or where the first intake air flow isless than the first baseline intake air flow and where the second intakeair flow is less than the second baseline intake air flow. A seventhexample of the method optionally includes any one or more or each of thefirst through sixth examples, and further includes wherein the thirdcondition and the fourth condition are conducted under conditions wheredegradation in the intake manifold, engine and exhaust system is notalready indicated; wherein the first condition, second condition, thirdcondition, and fourth condition are all conducted under conditions wherethe vehicle is not occupied and where the vehicle is not in motion; andwherein the first intake air flow, the first baseline intake air flow,the second intake air flow, and the second baseline intake air flow areindicated via a mass air flow sensor positioned in the intake manifoldof the engine, and where the first exhaust air flow and the firstbaseline exhaust air flow are indicated via a differential pressuresensor positioned in the exhaust system.

An example of a system for a vehicle comprises an engine systemincluding an intake manifold, an exhaust system, and an engine; a massair flow sensor positioned in the intake manifold; a motor, capable orrotating the engine unfueled; and a controller, storing instructions innon-transitory memory that, when executed, cause the controller to:obtain a first baseline intake air flow via the mass air flow sensor byrotating the engine unfueled via the motor in a forward direction andobtain a second baseline intake air flow via the mass air flow sensor byrotating the engine unfueled via the motor in a reverse direction, justsubsequent to rotating the engine unfueled in the forward direction toobtain the first baseline intake air flow; and responsive to conditionsbeing indicated to be met for conducting an engine system diagnostic toindicate a presence or absence of degradation stemming from the intakemanifold, engine, or exhaust system, obtain a first intake air flow viathe mass air flow sensor by rotating the engine unfueled via the motorin the forward direction and obtain a second intake air flow via themass air flow sensor by rotating the engine unfueled via the motor inthe reverse direction just subsequent to rotating the engine unfueled inthe forward direction to obtain the first intake air flow, and whereindicating the presence or absence of degradation involves comparing thefirst intake air flow to the first baseline intake air flow to yield afirst result, comparing the second intake air flow to the secondbaseline intake air flow to yield a second result, and then comparingthe first result to the second result to pinpoint whether degradation ispresent in the intake manifold, the engine, or the exhaust system. In afirst example of the system, the system further includes wherein thecontroller stores further instructions to indicate degradation stemmingfrom the intake manifold when the first result includes the first intakeair flow being substantially equivalent to the first baseline intake airflow, but where the second result includes the second intake air flowbeing less than the second baseline intake air flow; indicatedegradation stemming from the exhaust system when the first resultincludes the first intake air flow being substantially equivalent to thefirst baseline intake air flow, but where the second result includes thesecond intake air flow is greater than the second baseline intake airflow; indicate degradation stemming from the engine when the firstresult includes the first intake air flow being less than the firstbaseline intake air flow, and where the second result includes thesecond intake air flow being less than the second baseline intake airflow; and indicate the absence of degradation stemming from the intakemanifold, the engine, or the exhaust system when the first resultincludes the first intake air flow being substantially equivalent to thefirst baseline intake air flow, and where the second result includes thesecond intake air flow being substantially equivalent to the secondbaseline intake air flow. A second example of the system optionallyincludes the first example, and further comprises one or more of seatload cells, door sensing technology, and/or onboard cameras, where theseat load cells, door sensing technology and/or onboard cameras areconfigured to provide information on vehicle operator and passengeroccupancy of the vehicle; and wherein the controller stores furtherinstructions to obtain the first baseline intake air flow and the secondbaseline intake air flow provided there is not already an indication ofdegradation in the intake manifold, the engine, or the exhaust system;and wherein obtaining the first baseline intake air flow, obtaining thefirst intake air flow, obtaining the second baseline intake air flow,and obtaining the second intake air flow are conducted under conditionswhere the vehicle is indicated to be unoccupied.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method comprising: routing a first airflow through an intake of an engine, an intake manifold of the engine,the engine, and an exhaust system of the engine, in that order, in afirst condition; routing a second air flow through the exhaust system,the engine, the intake manifold, and the intake, in that order, in asecond condition; indicating a first intake air flow in the firstcondition and a second intake air flow in the second condition;indicating a first exhaust air flow in the first condition; anddiagnosing a presence or an absence of degradation stemming from one ofthe intake manifold, the engine, or the exhaust system as a function oftwo or more of the first intake air flow, the second intake air flow,and/or the first exhaust air flow.
 2. The method of claim 1, furthercomprising: in a third condition, indicating a first baseline intake airflow and indicating a first baseline exhaust air flow; in a fourthcondition, indicating a second baseline intake air flow; and wherein thethird condition includes routing a third air flow through the intake ofthe engine, the intake manifold of the engine, the engine, and theexhaust system of the engine, in that order; and wherein the fourthcondition includes routing a fourth air flow through the exhaust system,the engine, the intake manifold, and the intake, in that order.
 3. Themethod of claim 2, wherein the first condition and the third conditioninclude rotating the engine unfueled via a motor in a forward directionto route the first air flow through the intake, the intake manifold, theengine, and the exhaust system, in that order, and where the secondcondition and the fourth condition include rotating the engine unfueledvia the motor in a reverse direction to route the second air flowthrough the exhaust system, the engine, the intake manifold, and theintake, in that order.
 4. The method of claim 2, wherein routing thefirst air flow includes routing the first air flow for a firstpredetermined duration, and where routing the third air flow includesrouting the third air flow for the first predetermined duration; whereinrouting the second air flow includes routing the second air flow for asecond predetermined duration, where routing the fourth air flowincludes routing the fourth air flow for the second predeterminedduration, where the first predetermined duration is either the same ordifferent than the second predetermined duration; wherein each of thefirst condition, the second condition, the third condition, and thefourth condition includes controlling a throttle position in the intakeof a vehicle to a predetermined open position; and wherein each of thefirst condition, the second condition, the third condition, and thefourth condition includes sealing an evaporative emissions system fromthe intake, the intake manifold, the engine, and the exhaust system, theevaporative emissions system configured to capture and store fuel vaporsfrom a fuel system of the vehicle, and wherein each of the firstcondition, the second condition, the third condition, and the fourthcondition includes sealing the intake, the intake manifold, the engine,and the exhaust system from an exhaust gas recirculation system, theexhaust gas recirculation system configured to route at least a portionof exhaust gases from the engine to the intake manifold.
 5. The methodof claim 2, further comprising: indicating the presence of degradationstemming from the intake manifold responsive to the first intake airflow being substantially equivalent to the first baseline intake airflow and where the first exhaust air flow is greater than the firstbaseline exhaust air flow, and/or where the first intake air flow issubstantially equivalent to the first baseline intake air flow and wherethe second intake air flow is less than the second baseline intake airflow.
 6. The method of claim 2, further comprising: indicating thepresence of degradation stemming from the exhaust system responsive tothe first intake air flow being substantially equivalent to the firstbaseline intake air flow and where the first exhaust air flow is lessthan the first baseline exhaust air flow, and/or where the first intakeair flow is substantially equivalent to the first baseline intake airflow and where the second intake air flow is greater than the secondbaseline intake air flow.
 7. The method of claim 2, further comprising:indicating the presence of degradation stemming from the engineresponsive to the first intake air flow being less than the firstbaseline intake air flow and responsive to the first exhaust air flowbeing less than the first baseline exhaust air flow, and/or where thefirst intake air flow is less than the first baseline intake air flowand where the second intake air flow is less than the second baselineintake air flow.
 8. The method of claim 2, wherein the third conditionand the fourth condition are conducted under conditions wheredegradation in the intake manifold, the engine, and the exhaust systemis not already indicated; wherein the first condition, the secondcondition, the third condition, and the fourth condition are allconducted under conditions where a vehicle is not occupied and where thevehicle is not in motion; and wherein the first intake air flow, thefirst baseline intake air flow, the second intake air flow, and thesecond baseline intake air flow are indicated via a mass air flow sensorpositioned in the intake manifold of the engine, and where the firstexhaust air flow and the first baseline exhaust air flow are indicatedvia a differential pressure sensor positioned in the exhaust system.